tests: correct skipif sense

[martin-kokos]

What does this PR do?

Tests are skipped even if though the libs they use are installed. Check appears to be inverted by accident.
Fixes inverted skipif check.

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

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📚 Documentation preview 📚: https://torchmetrics--2931.org.readthedocs.build/en/2931/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 36%. Comparing base (767c678) to head (dcfe914).
Report is 8 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (767c678) and HEAD (dcfe914). Click for more details.

HEAD has 212 uploads less than BASE

Flag	BASE (767c678)	HEAD (dcfe914)
macOS	16	4
python3.11	16	4
cpu	68	17
torch2.6.0	4	1
torch2.6.0+cpu	8	2
Windows	12	3
python3.12	12	3
torch2.5.0	4	1
python3.10	36	9
torch2.0.1	8	2
torch2.0.1+cpu	12	3
torch2.5.0+cpu	12	3
Linux	40	10
torch2.4.1+cpu	8	2
torch2.2.2+cpu	4	1
python3.9	4	1
torch2.3.1+cpu	4	1
gpu	4	0
unittest	4	0
torch2.1.2+cpu	4	1

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #2931     +/-   ##
========================================
- Coverage      69%     36%    -33%     
========================================
  Files         346     332     -14     
  Lines       19172   18996    -176     
========================================
- Hits        13236    6773   -6463     
- Misses       5936   12223   +6287