Fix local test test_get_remote fail

[Mecoli1219]

Tracking issue

flyteorg/flyte#5687

Why are the changes needed?

FlytekitPlugin.get_remote(None, ...) will call get_config_file if the first argument is None.
As described in #2705, get_config_file will not always return None in developers' local environments.

What changes were proposed in this pull request?

Add a mock function that forces the return value of get_config_file to None.

How was this patch tested?

make unit_test

Setup process

Run it locally

Screenshots

I'll open other PRs to fix the other 2 unit tests.

Check all the applicable boxes

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

Related PRs

#2705
#2707

Docs link

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 48.67%. Comparing base (a8f68d7) to head (319e637).
Report is 13 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (a8f68d7) and HEAD (319e637). Click for more details.

HEAD has 17 uploads less than BASE

Flag	BASE (a8f68d7)	HEAD (319e637)
	32	15

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #2706       +/-   ##
===========================================
- Coverage   78.91%   48.67%   -30.25%     
===========================================
  Files         316      253       -63     
  Lines       24965    22401     -2564     
  Branches     4012     2773     -1239     
===========================================
- Hits        19702    10904     -8798     
- Misses       4548    11388     +6840     
+ Partials      715      109      -606     

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