Use PostgreSQL 9.6.11 in CI tests

Specify the minor version of postgresql for CI
Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

.gitlab/ci/frontend.gitlab-ci.yml

@@ -8,7 +8,7 @@
 
 .use-pg: &use-pg
   services:
-    - name: postgres:9.6
+    - name: postgres:9.6.11
       command: ["postgres", "-c", "fsync=off", "-c", "synchronous_commit=off", "-c", "full_page_writes=off"]
     - name: redis:alpine
 

.gitlab/ci/rails.gitlab-ci.yml

 .use-pg: &use-pg
   services:
-    - name: postgres:9.6
+    - name: postgres:9.6.11
       command: ["postgres", "-c", "fsync=off", "-c", "synchronous_commit=off", "-c", "full_page_writes=off"]
     - name: redis:alpine
 

changelogs/unreleased/use-pg-9-6-11-on-ci.yml

+---
+title: Use PostgreSQL 9.6.11 in CI tests
+merge_request: 30270
+author: Takuya Noguchi
+type: other