Update build container for public CI (#1233)

Author: NikolaMilosavljevic

azure-pipelines/templates/stages/build.yml

@@ -9,7 +9,7 @@ stages:
     pool:
       ${{ if eq(variables['System.TeamProject'], 'public') }}:
         name: $(DncEngPublicBuildPool)
-        demands: ImageOverride -equals Build.Ubuntu.1804.Amd64.Open
+        demands: ImageOverride -equals Build.Ubuntu.2204.Amd64.Open
       ${{ if eq(variables['System.TeamProject'], 'internal') }}:
         name: $(DncEngInternalBuildPool)
         image: 1es-ubuntu-2204