Use markdown syntax

Author: utpilla

opentelemetry-sdk/src/metrics/test.md

@@ -4,23 +4,21 @@ Tests are located in [mod.rs](mod.rs)
 
 // TODO: Fill this correctly.
 
-:heavy_check_mark: 
-
 ## Sync Instruments
 
 | Test Type                  | Counter (Delta) | Counter (Cumulative) | UpDownCounter (Delta) | UpDownCounter (Cumulative) | Gauge (Delta) | Gauge (Cumulative) | Histogram (Delta) | Histogram (Cumulative) |
 |----------------------------|-----------------|----------------------|----------------------|----------------------------|---------------|--------------------|-------------------|------------------------|
-| Regular aggregation test   | ✅        | ✅              | ❌              | ❌                    | ❌      | ❌            | ❌           | ❌                |
-| No-attribute test          | ✅         | ✅              | ❌              | ❌                    | ❌      | ❌            | ❌           | ❌                |
-| Overflow test              | ✅         | ✅              | ❌              | ❌                    | ❌      | ❌            | ❌           | ❌                |
-| Attr Order Sorted First    | ✅         | ✅              | ❌              | ❌                    | ❌      | ❌            | ❌           | ❌                |
-| Attr Order Unsorted First  | ✅         | ✅              | ❌              | ❌                    | ❌      | ❌            | ❌           | ❌                |
+| Regular aggregation test   | :white_check_mark:       | :white_check_mark:             | :x:              | :x:                    | :x:      | :x:            | :x:           | :x:                |
+| No-attribute test          | :white_check_mark:        | :white_check_mark:             | :x:              | :x:                    | :x:      | :x:            | :x:           | :x:                |
+| Overflow test              | :white_check_mark:        | :white_check_mark:             | :x:              | :x:                    | :x:      | :x:            | :x:           | :x:                |
+| Attr Order Sorted First    | :white_check_mark:        | :white_check_mark:             | :x:              | :x:                    | :x:      | :x:            | :x:           | :x:                |
+| Attr Order Unsorted First  | :white_check_mark:        | :white_check_mark:             | :x:              | :x:                    | :x:      | :x:            | :x:           | :x:                |
 
 ## Observable Instruments
 
 | Test Type                  | ObservableCounter (Delta) | ObservableCounter (Cumulative) | ObservableGauge (Delta) | ObservableGauge (Cumulative) | ObservableUpDownCounter (Delta) | ObservableUpDownCounter (Cumulative) |
 |----------------------------|---------------------------|-------------------------------|-------------------------|------------------------------|---------------------------------|--------------------------------------|
-| Regular aggregation test    | ❌                  | ❌                      | ❌                | ❌                     | ❌                        | ❌                             |
-| No-attribute test           | ❌                  | ❌                      | ❌                | ❌                     | ❌                        | ❌                             |
-| Attr Order Sorted First    | ✅         | ✅              | ❌              | ❌                    | ❌      | ❌            | ❌           | ❌                |
-| Attr Order Unsorted First  | ✅         | ✅              | ❌              | ❌                    | ❌      | ❌            | ❌           | ❌                |
+| Regular aggregation test    | :x:                  | :x:                      | :x:                | :x:                     | :x:                        | :x:                             |
+| No-attribute test           | :x:                  | :x:                      | :x:                | :x:                     | :x:                        | :x:                             |
+| Attr Order Sorted First    | :white_check_mark:        | :white_check_mark:             | :x:              | :x:                    | :x:      | :x:            | :x:           | :x:                |
+| Attr Order Unsorted First  | :white_check_mark:        | :white_check_mark:             | :x:              | :x:                    | :x:      | :x:            | :x:           | :x:                |