CI: update Github Action runner Ubuntu versions to 22.04

We were all over the place with these, with some going all the way back to Ubuntu 16!

Connects pelias/pelias#951

Author: orangejulius

.github/workflows/elasticsearch-image-builder.yml

@@ -7,7 +7,7 @@
 # jobs:
 #   build:
 #     if: github.ref == 'refs/heads/master' && needs.unit-tests.result == 'success'
-#     runs-on: ubuntu-20.04
+#     runs-on: ubuntu-22.04
 #     strategy:
 #       matrix:
 #         elastic-version: