Update to ubuntu-latest for all non-backwards compat workflows (#5450)

The runner image `ubuntu-20.04` "will be fully retired by April 1, 2025"


https://github.blog/changelog/2025-01-15-github-actions-ubuntu-20-runner-image-brownout-dates-and-other-breaking-changes/

And there are multiple brownout periods in March. This PR is an attempt
to avoid unnecessary failures during the brownouts. I updated all the
workflows to ubuntu-latest except those that were explicitly related to
testing for backwards compatibility, since that will require more
judgement on the oldest toolchain we continue to regularly test in CI.

---
TYPE: NO_HISTORY
DESC: Update to ubuntu-latest for all non-backwards compat workflows

.github/workflows/check-formatting.yml

@@ -19,7 +19,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     if: ${{ startsWith(github.ref , 'refs/tags') != true && startsWith(github.ref , 'build-') != true }}
     timeout-minutes: 90
     name: Check Clang Format

.github/workflows/check-heap-memory-api-violations.yml

@@ -17,7 +17,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     if: ${{ startsWith(github.ref , 'refs/tags') != true && startsWith(github.ref , 'build-') != true }}
     timeout-minutes: 90
     name: Check Heap Memory Violations

.github/workflows/check-pr-body.yml

@@ -12,7 +12,7 @@ on:
 
 jobs:
   check_pr_body:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - name: Check out the repository
         uses: actions/checkout@v3

.github/workflows/prepare-release.yml

@@ -12,7 +12,7 @@ on:
 
 jobs:
   prepare_release:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
 
     steps:
       - name: Check out the repository