fix(audit): Update audit-from-cache flag description

[ssheladiya]

What this PR does / why we need it:
Update audit-from-cache flag description to clearly let the users know about auditing from synced resources from the internal cache

Which issue(s) this PR fixes (optional, using fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when the PR gets merged):
Fixes #2948

Special notes for your reviewer:

[codecov-commenter]

Codecov Report

Patch coverage: 35.98% and project coverage change: -0.53% ⚠️

Comparison is base (e50ee2f) 53.07% compared to head (ad4e1a0) 52.54%.
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2989      +/-   ##
==========================================
- Coverage   53.07%   52.54%   -0.53%     
==========================================
  Files         135      134       -1     
  Lines       11813    11913     +100     
==========================================
- Hits         6270     6260      -10     
- Misses       5055     5165     +110     
  Partials      488      488              

Flag	Coverage Δ
unittests	52.54% <35.98%> (-0.53%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
pkg/audit/audit_cache_lister.go	0.00% <0.00%> (ø)
pkg/audit/manager.go	9.83% <ø> (ø)
pkg/cachemanager/aggregator/aggregator.go	77.31% <0.00%> (ø)
pkg/cachemanager/parser/syncannotationreader.go	91.42% <ø> (ø)
pkg/syncutil/stats_reporter.go	17.52% <0.00%> (-3.73%)	⬇️
pkg/cachemanager/cachemanager.go	39.92% <39.92%> (ø)
pkg/controller/config/config_controller.go	57.65% <57.14%> (-5.87%)	⬇️

... and 3 files with indirect coverage changes

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[acpana]

thanks for the PR 🥇

[maxsmythe]

LGTM

[sozercan]

thank you! LGTM