Change no-unused-vars lint rule to a warning

[Tyriar]

It's quite distracting having an unused variable error appear, this should be a warning as it's normally just a dev time thing. Committing should reject all warnings anyway.

[codecov-commenter]

Codecov Report

Merging #12048 (3bd8742) into main (503220a) will increase coverage by 15%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##            main   #12048     +/-   ##
========================================
+ Coverage     47%      62%    +15%     
========================================
  Files        502      502             
  Lines      35918    35918             
  Branches    5813     5813             
========================================
+ Hits       16908    22594   +5686     
+ Misses     17399    11193   -6206     
- Partials    1611     2131    +520     

Impacted Files	Coverage Δ
src/platform/common/platform/fs-paths.node.ts	64% <0%> (ø)
src/platform/vscode-path/map.ts	10% <0%> (+<1%)	⬆️
src/platform/logging/index.ts	75% <0%> (+<1%)	⬆️
src/kernels/serviceRegistry.node.ts	100% <0%> (+1%)	⬆️
...platform/interpreter/reservedNamedProvider.node.ts	93% <0%> (+1%)	⬆️
src/platform/vscode-path/resources.ts	40% <0%> (+1%)	⬆️
...ernels/raw/session/hostRawNotebookProvider.node.ts	86% <0%> (+1%)	⬆️
src/kernels/kernelProvider.node.ts	100% <0%> (+1%)	⬆️
src/platform/common/utils.ts	79% <0%> (+1%)	⬆️
...preter/jupyterInterpreterDependencyService.node.ts	75% <0%> (+1%)	⬆️
... and 271 more