fix(ext.bridge): Handle BridgeCommand while unloading cogs

[OmLanke]

Summary

Remove BridgeCommand correctly

Fixes #1899

Information

• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed).
• This PR is not a code change (e.g. documentation, README, typehinting,
  examples, ...).

Checklist

• I have searched the open pull requests for duplicates.
• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why.
• I have updated the changelog to include these changes.

[codecov]

Codecov Report

Merging #2048 (cc625ae) into master (ea3e3db) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2048      +/-   ##
==========================================
- Coverage   33.24%   33.24%   -0.01%     
==========================================
  Files          97       97              
  Lines       19033    19036       +3     
==========================================
  Hits         6328     6328              
- Misses      12705    12708       +3     

Flag	Coverage Δ
macos-latest-3.10	33.22% <0.00%> (-0.01%)	⬇️
macos-latest-3.11	33.22% <0.00%> (-0.01%)	⬇️
macos-latest-3.8	33.23% <0.00%> (-0.01%)	⬇️
macos-latest-3.9	33.23% <0.00%> (-0.01%)	⬇️
ubuntu-latest-3.10	33.22% <0.00%> (-0.01%)	⬇️
ubuntu-latest-3.11	33.22% <0.00%> (-0.01%)	⬇️
ubuntu-latest-3.8	33.23% <0.00%> (-0.01%)	⬇️
ubuntu-latest-3.9	33.23% <0.00%> (-0.01%)	⬇️
windows-latest-3.10	33.22% <0.00%> (-0.01%)	⬇️
windows-latest-3.11	33.22% <0.00%> (-0.01%)	⬇️
windows-latest-3.8	33.23% <0.00%> (-0.01%)	⬇️
windows-latest-3.9	33.23% <0.00%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
discord/cog.py	34.64% <0.00%> (-0.28%)	⬇️

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