chore(ci): Update markdown-checks.yml

Author: averikitsch

.github/workflows/markdown-checks.yml

@@ -30,4 +30,4 @@ jobs:
         uses: lycheeverse/lychee-action@885c65f3dc543b57c898c8099f4e08c8afd178a2 # v2.6.1
         with:
           # There is no security token. So, it would fail on any links which aren't public.
-          args: "--verbose --no-progress **/*.md"
+          args: "--verbose --no-progress README.md CLOUD-SQL-POSTGRESQL.md"