ci: update runs-on to ubuntu-latest

This commit updates the `runs-on` configuration in the CI workflows (`ci.yml`, `pr.yml`) from specific `ubuntu-latest-Xcore` labels to the more general `ubuntu-latest`. This change reduces resource consumption. This change should not be needed for RBE and remote cache.

Author: alan-agius4

.github/workflows/ci.yml

@@ -58,7 +58,7 @@ jobs:
 
   test:
     needs: build
-    runs-on: ubuntu-latest-4core
+    runs-on: ubuntu-latest
     steps:
       - name: Initialize environment
         uses: angular/dev-infra/github-actions/npm/checkout-and-setup-node@3186a078ec23edea6e2f6192ed013ec57bd95f87

.github/workflows/pr.yml

@@ -90,7 +90,7 @@ jobs:
 
   test:
     needs: build
-    runs-on: ubuntu-latest-16core
+    runs-on: ubuntu-latest
     steps:
       - name: Initialize environment
         uses: angular/dev-infra/github-actions/npm/checkout-and-setup-node@3186a078ec23edea6e2f6192ed013ec57bd95f87