revert: Drop upstreamed PerfPowerServices macos-15-intel fixes

[matthewfeickert]

Description

• Remove macos-15-intel specific runner fixes as they have been upstreamed into GitHub Actions runners.
  • c.f. macos-15 (20251210) Image Update actions/runner-images#13414
  • macos-15-intel slow, always 100% CPU? actions/runner-images#13358
• Reverts PR ci: Disable PerfPowerServices process on macos-15-intel #2641

Checklist Before Requesting Reviewer

• Tests are passing
• "WIP" removed from the title of the pull request
• Selected an Assignee for the PR to be responsible for the log summary

Before Merging

For the PR Assignees:

• Summarize commit messages into a comprehensive review of the PR

* Remove macos-15-intel specific runner fixes as they have been upstreamed
  into GitHub Actions runners.
   - c.f. https://github.com/actions/runner-images/pull/13414
* Reverts PR https://github.com/scikit-hep/pyhf/pull/2641

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.23%. Comparing base (9dd6a2c) to head (54265ba).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2644   +/-   ##
=======================================
  Coverage   98.23%   98.23%           
=======================================
  Files          65       65           
  Lines        4190     4190           
  Branches      453      453           
=======================================
  Hits         4116     4116           
  Misses         45       45           
  Partials       29       29           

Flag	Coverage Δ
contrib	98.11% <ø> (ø)
doctest	98.23% <ø> (ø)
unittests-3.10	96.42% <ø> (ø)
unittests-3.11	96.42% <ø> (ø)
unittests-3.12	96.42% <ø> (ø)
unittests-3.13	96.42% <ø> (ø)
unittests-3.9	96.46% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.