chore(deps): update ghcr.io/cloudnative-pg/postgresql docker tag (#67)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/build.yaml

@@ -18,17 +18,17 @@ jobs:
         include:
           - postgres_version: "17"
             # renovate datasource=docker depName=ghcr.io/cloudnative-pg/postgresql
-            cnpg_version: 17.2-20
+            cnpg_version: 17.2-21
             latest: "true"
           - postgres_version: "16"
             # renovate datasource=docker depName=ghcr.io/cloudnative-pg/postgresql
-            cnpg_version: 16.6-20
+            cnpg_version: 16.6-21
           - postgres_version: "15"
             # renovate datasource=docker depName=ghcr.io/cloudnative-pg/postgresql
-            cnpg_version: 15.10-20
+            cnpg_version: 15.10-21
           - postgres_version: "14"
             # renovate datasource=docker depName=ghcr.io/cloudnative-pg/postgresql
-            cnpg_version: 14.15-20
+            cnpg_version: 14.15-21
     steps:
       - name: Checkout
         uses: actions/checkout@v4