Remove learning rate adjustment and notice

[pmachapman]

As the 60 days have passed and Serval automatically sets this rate for us, this PR reverts the following PRs:

• SF-3063 Specify updated learning rate for Serval #2829
• Add messaging for adjusted learning rate schedule #2832
• Hide learning rate notice after 60 days #2902

The feature flag is retained so an version numbers with the feature flag will be parsed correctly.

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This change is 

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.90%. Comparing base (53fa502) to head (e9224d5).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2933      +/-   ##
==========================================
- Coverage   80.91%   80.90%   -0.01%     
==========================================
  Files         533      533              
  Lines       31225    31204      -21     
  Branches     5085     5082       -3     
==========================================
- Hits        25267    25247      -20     
  Misses       5198     5198              
+ Partials      760      759       -1     

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[josephmyers]

Reviewed 9 of 9 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @pmachapman)