Update postgres Docker tag to v18

| datasource | package  | from | to   |
| ---------- | -------- | ---- | ---- |
| docker     | postgres | 17.6 | 18.0 |


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

Author: renovate[bot]

.github/workflows/benchmark.yml

@@ -14,7 +14,7 @@ jobs:
     services:
       postgres:
         # Docker Hub image
-        image: "postgres:17.6"
+        image: "postgres:18.0"
         # Provide the password for postgres
         env:
           POSTGRES_PASSWORD: postgres