[CI] Replace rules usage with only/except to correctly run nightlies

Author: Mordil

.gitlab/ci/centos-7.yml

@@ -11,8 +11,7 @@ include: '/.gitlab/ci/platform-test.yml'
 swift trunk:
   extends: .centos7
   image: swiftlang/swift:nightly-master-centos7
-  variables:
-    RUN_NIGHTLY: 1
+  except:
 
 swift 5.5:
   extends: .centos7

.gitlab/ci/platform-test.yml

@@ -15,10 +15,9 @@ stages:
   script:
     - swift build --build-tests --enable-test-discovery --sanitize=thread -v 
     - swift test --skip-build
-  rules:
-    - if: '$CI_PIPELINE_SOURCE == "schedule" && $RUN_NIGHTLY'
-      allow_failure: true
-      when: always
-    - if: '$CI_PIPELINE_SOURCE != "schedule"'
-      when: always
+  only:
+    - branches
+    - tags
+  except:
+    - schedules
 

.gitlab/ci/standard-platforms.yml

@@ -3,8 +3,7 @@ include: '/.gitlab/ci/platform-test.yml'
 swift trunk:
   extends: .platform-test
   image: swiftlang/swift:nightly-master-${SWIFT_PLATFORM_NAME}
-  variables:
-    RUN_NIGHTLY: 1
+  except:
 
 swift 5.5:
   extends: .platform-test