Switch ubuntu-20.04 to ubuntu-latest

The current version has been retired
https://ubuntu.com/about/release-cycle

Signed-off-by: Petr "Stone" Hracek <[email protected]>

Author: phracek

.github/workflows/build-and-push.yml

@@ -9,7 +9,7 @@ on:
 jobs:
   build-and-push:
     if: github.repository_owner == 'sclorg'
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:

.github/workflows/container-tests.yml

@@ -4,7 +4,7 @@ on:
       - created
 jobs:
   container-tests:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     name: "Container tests: ${{ matrix.version }} - ${{ matrix.os_test }}"
     concurrency:
       group: container-${{ github.event.issue.number }}-${{ matrix.version }}-${{ matrix.os_test }}