Apply manual on the job instead of in job:rules so that's it's optional instead of blocking

.gitlab-ci.yml

@@ -49,8 +49,7 @@ build:python2.7:
 
 build:2.10:
   extends: .build
-  rules:
-    - when: manual
+  when: manual
   allow_failure: false
   variables:
     ALPINE_VERSION: 3.14
@@ -59,8 +58,7 @@ build:2.10:
 
 build:2.9:
   extends: .build
-  rules:
-    - when: manual
+  when: manual
   allow_failure: false
   variables:
     ALPINE_VERSION: 3.12