Update nightly-tests.yml

Author: mmulji-ic

.github/workflows/nightly-tests.yml

@@ -12,7 +12,7 @@ jobs:
     uses: cosmos/gaia/.github/workflows/test.yml@main
     strategy:
       fail-fast: false
-      max-parallel: 3
+      max-parallel: 1
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]       # We can add custom runners - https://github.com/actions/runner