fix the exception occurred when publish/rollback namespaces with grayrelease

[nobodyiam]

What's the purpose of this PR

fix the exception occurred when publish/rollback namespaces with grayrelease

Which issue(s) this PR fixes:

Fixes #4563

Brief changelog

• revert the OPERATION_CONTEXT_TYPE_REFERENCE to new TypeToken<Map<String, Object>>() { }.getType()

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[codecov-commenter]

Codecov Report

Merging #4564 (c43bd70) into master (b344d54) will increase coverage by 0.03%.
The diff coverage is 33.33%.

@@             Coverage Diff              @@
##             master    #4564      +/-   ##
============================================
+ Coverage     53.28%   53.31%   +0.03%     
  Complexity     2711     2711              
============================================
  Files           495      495              
  Lines         15438    15437       -1     
  Branches       1599     1599              
============================================
+ Hits           8226     8231       +5     
+ Misses         6652     6646       -6     
  Partials        560      560              

Impacted Files	Coverage Δ
...p/framework/apollo/biz/service/ReleaseService.java	71.87% <33.33%> (+0.27%)	⬆️
...ervice/service/ReleaseMessageServiceWithCache.java	85.88% <0.00%> (-1.18%)	⬇️
.../apollo/internals/RemoteConfigLongPollService.java	78.44% <0.00%> (+1.19%)	⬆️
...ework/apollo/internals/RemoteConfigRepository.java	87.73% <0.00%> (+2.45%)	⬆️

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[mghio]

LGTM.