bench: mark test_get/import as flaky

[efiop]

Sometimes seeing those error out in 2.x and early 3.x with:

ERROR: unexpected error - [Errno 95] no more link types left to try out: [Errno 95] Operation not supported

It seems like we've fixed it at some point, but I was not able to quickly find a link. Will update this if I do.

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (7c898cf) 90.64% compared to head (1c77d4e) 90.38%.

Files	Patch %	Lines
dvc/testing/benchmarks/cli/commands/test_get.py	0.00%	2 Missing ⚠️
dvc/testing/benchmarks/cli/commands/test_import.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10148      +/-   ##
==========================================
- Coverage   90.64%   90.38%   -0.26%     
==========================================
  Files         496      496              
  Lines       37747    37751       +4     
  Branches     5488     5490       +2     
==========================================
- Hits        34215    34121      -94     
- Misses       2896     2971      +75     
- Partials      636      659      +23     

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[efiop]

Thanks to @skshetry for finding it #9512 1d47b03#commitcomment-134529297