[flyteagent] Remove redundant code in Agent

[Future-Outlier]

Tracking issue

#3936

Why are the changes needed?

Comment in the description below.

What changes were proposed in this pull request?

How was this patch tested?

single binary.

Setup process

Screenshots

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 4 lines in your changes missing coverage. Please review.

Project coverage is 61.01%. Comparing base (25c3596) to head (fce16bf).
Report is 142 commits behind head on master.

Files with missing lines	Patch %	Lines
...yteplugins/go/tasks/plugins/webapi/agent/client.go	50.00%	1 Missing and 1 partial ⚠️
...yteplugins/go/tasks/plugins/webapi/agent/plugin.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5454      +/-   ##
==========================================
- Coverage   61.07%   61.01%   -0.07%     
==========================================
  Files         793      793              
  Lines       51226    51289      +63     
==========================================
+ Hits        31288    31292       +4     
- Misses      17062    17119      +57     
- Partials     2876     2878       +2     

Flag	Coverage Δ
unittests-datacatalog	69.31% <ø> (ø)
unittests-flyteadmin	58.66% <ø> (-0.25%)	⬇️
unittests-flytecopilot	17.79% <ø> (ø)
unittests-flytectl	67.97% <ø> (ø)
unittests-flyteidl	79.04% <ø> (ø)
unittests-flyteplugins	61.97% <33.33%> (+0.02%)	⬆️
unittests-flytepropeller	57.32% <ø> (ø)
unittests-flytestdlib	65.82% <ø> (ø)

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