chore: improve hover color in dark mode

[LucasXu0]

Feature Preview

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PR Checklist

• My code adheres to AppFlowy's Conventions
• I've listed at least one issue that this PR fixes in the description above.
• I've added a test(s) to validate changes in this PR, or this PR only contains semantic changes.
• All existing tests are passing.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.72%. Comparing base (94f9349) to head (1d6b1b4).
Report is 797 commits behind head on main.

❗ Current head 1d6b1b4 differs from pull request most recent head 1938518

Please upload reports for the commit 1938518 to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##            main    #5537       +/-   ##
==========================================
+ Coverage   9.70%   86.72%   +77.02%     
==========================================
  Files        685      219      -466     
  Lines      31812     5039    -26773     
  Branches       0      833      +833     
==========================================
+ Hits        3086     4370     +1284     
+ Misses     28726      562    -28164     
- Partials       0      107      +107     

Flag	Coverage Δ
appflowy_flutter_unit_test	?
appflowy_web_app	86.72% <ø> (?)

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