Removed futures-channel from opentelemetry dependencies

[shaun-cox]

Fixes #1201

Changes

Removed futures-channel from opentelemetry dependencies. It was only used for a few fallible conversions to LogError and TraceError types, only one of which was being used by opentelemetry-stackdriver.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (6603a58) 49.3% compared to head (53439f3) 49.3%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #1229   +/-   ##
=====================================
  Coverage   49.3%   49.3%           
=====================================
  Files        173     173           
  Lines      20978   20968   -10     
=====================================
  Hits       10349   10349           
+ Misses     10629   10619   -10     

Files Changed	Coverage Δ
opentelemetry-stackdriver/src/lib.rs	30.8% <0.0%> (-0.1%)	⬇️
opentelemetry/src/logs/mod.rs	0.0% <ø> (ø)
opentelemetry/src/trace/mod.rs	92.6% <ø> (+11.8%)	⬆️

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[jtescher]

Thanks @shaun-cox