Revert "Update formatting CI check Github runnner to ubuntu-latest"

This reverts commit 28ff474.

Author: tony-josi-aws

.github/workflows/ci.yml

@@ -131,7 +131,7 @@ jobs:
           exclude-dirs: source/portable/NetworkInterface/STM32
 
   formatting:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v4
       - name: Check formatting