Update docker.io/postgres Docker tag to v18

.gitea/workflows/lint-test-docker.yaml

@@ -17,7 +17,7 @@ on:
 
 jobs:
   docker-lint:
-    runs-on: ubuntu-24.04
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v4

.gitea/workflows/lint-test-helm.yaml

@@ -17,7 +17,7 @@ on:
 
 jobs:
   helm-lint:
-    runs-on: ubuntu-24.04
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v4

.gitea/workflows/renovate.yaml

@@ -12,7 +12,7 @@ on:
 
 jobs:
   renovate:
-    runs-on: ubuntu-24.04
+    runs-on: ubuntu-latest
     container: ghcr.io/renovatebot/renovate:41
     steps:
       - name: Checkout