chore(gitlab-ci): link postgres service to job

.gitlab-ci.yml

@@ -7,9 +7,6 @@ default:
       - .stack
       - .stack-work
       
-services:
-  - postgres:latest
-
 variables:
   STACK_ROOT: "${CI_PROJECT_DIR}/.stack"
   CHROME_BIN: "/usr/bin/chromium-browser"
@@ -177,6 +174,9 @@ hlint:
       - $CI_COMMIT_REF_NAME =~ /^v[0-9].*/
 
 yesod:test:
+  services:
+    - postgres:10.10
+
   stage: test
   script:
     - stack test --coverage --flag uniworx:-library-only --flag uniworx:-dev --flag uniworx:pedantic --skip hlint