style: change homepage leftbar font color

[nisiyong]

What's the purpose of this PR

Currently, this font color is a little out of fit. I think make it as same with the button color will be better.

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[codecov]

Codecov Report

Merging #4781 (b797d42) into master (ce1c2f8) will increase coverage by 0.03%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #4781      +/-   ##
============================================
+ Coverage     47.26%   47.29%   +0.03%     
- Complexity     1657     1660       +3     
============================================
  Files           346      346              
  Lines         10683    10683              
  Branches       1063     1063              
============================================
+ Hits           5049     5053       +4     
+ Misses         5328     5322       -6     
- Partials        306      308       +2     

Impacted Files	Coverage Δ
...mework/apollo/openapi/service/ConsumerService.java	58.46% <0.00%> (+1.53%)	⬆️
...framework/apollo/openapi/entity/ConsumerAudit.java	48.48% <0.00%> (+6.06%)	⬆️

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[nobodyiam]

LGTM