ci: Fix labels on runs-on stanza such that they use Linux instead of linux

[rbarkerSL]

Description:

replace the linux label with Linux on the self-hosted runner runs-on stanza.

Related issue(s):

Fixes #8627

Notes for reviewer:

labels are case insensitive, the update is more for consistency.

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.40%. Comparing base (ce4f947) to head (1e8ef48). Report is 3 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #8628 +/- ## ============================================ + Coverage 92.39% 92.40% +0.01% Complexity 7489 7489 ============================================ Files 914 914 Lines 29854 29854 Branches 3640 3640 ============================================ + Hits 27584 27587 +3 + Misses 1444 1441 -3 Partials 826 826 ```

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