cleanup: remove all references to mobile-staging

Part of https://github.com/ooni/probe/issues/1440

.github/workflows/android.yml

@@ -2,7 +2,6 @@ name: android
 on:
   push:
     branches:
-      - mobile-staging
       - "release/**"
 jobs:
   test:

.github/workflows/codeql-analysis.yml

@@ -7,7 +7,7 @@ name: "CodeQL"
 
 on:
   push:
-    branches: [ master, mobile-staging, 'release/**' ]
+    branches: [ master, 'release/**' ]
   pull_request:
     # The branches below must be a subset of the branches above
     branches: [ master ]

.github/workflows/ios.yml

@@ -2,7 +2,6 @@ name: ios
 on:
   push:
     branches:
-      - mobile-staging
       - 'release/**'
 jobs:
   test: