NR-403516: move all pipelines from ubuntu-20 runners to ubuntu-latest

Author: muruganishekar

.github/workflows/prerelease.yml

@@ -13,7 +13,7 @@ env:
 jobs:
   test-integration-nix:
     name: Run integration tests on *Nix
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     defaults:
       run:
         working-directory: src/github.com/${{env.ORIGINAL_REPO_NAME}}

.github/workflows/push_pr.yml

@@ -14,7 +14,7 @@ jobs:
   # can't run this step inside of container because of tests specific
   test-integration-nix:
     name: Run integration tests on *Nix
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     defaults:
       run:
         working-directory: src/github.com/${{env.ORIGINAL_REPO_NAME}}