Changed Mac version

Signed-off-by: Amulya Varote <amulyavarote@microsoft.com>

.github/workflows/validate_new_quickstarts_pubsub.yaml

@@ -40,12 +40,12 @@ jobs:
       KIND_IMAGE_SHA: sha256:69860bda5563ac81e3c0057d654b5253219618a22ec3a346306239bba8cfa1a6
     strategy:
       matrix: 
-        os: [ubuntu-latest, macos-10.15]
+        os: [ubuntu-latest, macos-latest]
         quickstart_language: [go, javascript, python, java]
         quickstart_variant: [http, sdk]
     steps:
       - name: Install docker - MacOS
-        if: matrix.os == 'macos-10.15'
+        if: matrix.os == 'macos-latest'
         run: |
           /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"
           brew install --cask docker