ci: run parametric on ubuntu-latest machine (#14259)

CI: Downgrade the runner for parametric system tests, increasing a bit
the time it takes to run, but saving costs

## Checklist
- [x] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [x] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Author: gnufede

.github/workflows/system-tests.yml

@@ -260,8 +260,7 @@ jobs:
 
 
   parametric:
-    runs-on:
-      group: "APM Larger Runners"
+    runs-on: ubuntu-latest
     env:
       TEST_LIBRARY: python
     steps:
@@ -313,4 +312,4 @@ jobs:
         run: exit 0
       - name: Fails if anything else failed
         if: needs.parametric.result != 'success' || needs.system-tests.result != 'success'
-        run: exit 1
+        run: exit 1