ci: Fix missing labels format in dependabot file

[germa89]

Description

As the title.

Issue linked

NA

Checklist

• I have visited and read Develop PyMAPDL.
• I have tested my changes locally
• I have added necessary documentation or updated existing documentation.
• I have followed the PyMAPDL coding style guidelines.
• I have added appropriate unit tests that also ensure the minimal coverage criteria.
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved to the PR if any.
• I have assigned this PR to myself.
• I have marked this PR as draft if it is not ready to be reviewed yet.
• I have made sure that the title of my PR follows Commit naming conventions (e.g. feat: adding new MAPDL command)

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.21%. Comparing base (7c1eb1e) to head (9b40ba1).
Report is 19 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3204      +/-   ##
==========================================
- Coverage   86.63%   84.21%   -2.43%     
==========================================
  Files          52       53       +1     
  Lines        9550     9625      +75     
==========================================
- Hits         8274     8106     -168     
- Misses       1276     1519     +243