Apply suggestions from code review

Author: xrmx

docs/runtime/cpython-metrics.md

@@ -36,7 +36,7 @@ This metric is [recommended][MetricRecommended].
 
 | Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
 | -------- | --------------- | ----------- | -------------- | --------- |
-| `cpython.gc.collections` | Counter | `{collection}` | The number of times a generation was collected since interpreter start. [1] | ![Development](https://img.shields.io/badge/-development-blue) |
+| `cpython.gc.collections` | Counter | `{collections}` | The number of times a generation was collected since interpreter start. [1] | ![Development](https://img.shields.io/badge/-development-blue) |
 
 **[1]:** This metric reports data from [`gc.stats()`](https://docs.python.org/3/library/gc.html#gc.get_stats)
 
@@ -72,7 +72,7 @@ This metric is [recommended][MetricRecommended].
 
 | Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
 | -------- | --------------- | ----------- | -------------- | --------- |
-| `cpython.gc.collected` | Counter | `{collection}` | The total number of objects collected inside a generation that have occurred since interpreter start. [1] | ![Development](https://img.shields.io/badge/-development-blue) |
+| `cpython.gc.collected` | Counter | `{object}` | The total number of objects collected inside a generation that have occurred since interpreter start. [1] | ![Development](https://img.shields.io/badge/-development-blue) |
 
 **[1]:** This metric reports data from [`gc.stats()`](https://docs.python.org/3/library/gc.html#gc.get_stats)