Refs #34851 -- Used PostgreSQL 13 for selenium tests.

Follow up to 2c6ebb65c9eb6b11347d907127b82d31e04569e5.

.github/workflows/schedule_tests.yml

@@ -76,7 +76,7 @@ jobs:
     name: Selenium tests, PostgreSQL
     services:
       postgres:
-        image: postgres:12-alpine
+        image: postgres:13-alpine
         env:
           POSTGRES_DB: django
           POSTGRES_USER: user

.github/workflows/selenium.yml

@@ -41,7 +41,7 @@ jobs:
     name: PostgreSQL
     services:
       postgres:
-        image: postgres:12-alpine
+        image: postgres:13-alpine
         env:
           POSTGRES_DB: django
           POSTGRES_USER: user