Sync client should call CloseSend when done sending

[RRap0so]

Tracking issue

Closes #5885

Why are the changes needed?

The Grpc client never closes send so the server is unable to move forward in the grpc streaming onComplete method. This change will inform the server that is done sending so it can properly move to the next step.

What changes were proposed in this pull request?

Move the closeSend after sending all the necessary things.

How was this patch tested?

Unit test

Setup process

Screenshots

Check all the applicable boxes

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

Related PRs

Docs link

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.

Project coverage is 36.71%. Comparing base (197ae13) to head (587e39d).
Report is 17 commits behind head on master.

Files with missing lines	Patch %	Lines
...yteplugins/go/tasks/plugins/webapi/agent/plugin.go	0.00%	6 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5884      +/-   ##
==========================================
+ Coverage   34.48%   36.71%   +2.23%     
==========================================
  Files        1138     1304     +166     
  Lines      102742   130081   +27339     
==========================================
+ Hits        35434    47764   +12330     
- Misses      63634    78147   +14513     
- Partials     3674     4170     +496     

Flag	Coverage Δ
unittests-datacatalog	51.58% <ø> (+0.21%)	⬆️
unittests-flyteadmin	54.41% <ø> (-1.19%)	⬇️
unittests-flytecopilot	11.73% <ø> (-0.45%)	⬇️
unittests-flytectl	62.40% <ø> (?)
unittests-flyteidl	6.89% <ø> (-0.29%)	⬇️
unittests-flyteplugins	53.62% <0.00%> (+0.27%)	⬆️
unittests-flytepropeller	42.84% <ø> (+0.82%)	⬆️
unittests-flytestdlib	54.78% <ø> (-0.57%)	⬇️

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[Future-Outlier]

Just tested it for backward compatibility, thank you @RRap0so