Fix add_to_spyder_UMR_excludelist for Spyder 6

[sldesnoo-Delft]

The import of qcodes fails with Spyder 6, because add_to_spyder_UMR_excludelist raises an exception.

This pull request fixes the code to work with Spyder 6.0.
I've removed a bit of old code that was only useful for Spyder 3.x

I don't think this is easy to test with an automatic test, because a test would require Spyder 6.

[sldesnoo-Delft]

@microsoft-github-policy-service agree

[codecov]

Codecov Report

Attention: Patch coverage is 3.70370% with 26 lines in your changes missing coverage. Please review.

Project coverage is 68.24%. Comparing base (ef66ccc) to head (5efe1e4).
Report is 322 commits behind head on main.

Files with missing lines	Patch %	Lines
src/qcodes/utils/spyder_utils.py	3.70%	26 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6544      +/-   ##
==========================================
- Coverage   69.33%   68.24%   -1.10%     
==========================================
  Files         340      340              
  Lines       31261    31268       +7     
==========================================
- Hits        21676    21340     -336     
- Misses       9585     9928     +343     

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