workflows: Run only on runners with android app keystore

.forgejo/workflows/build-debug.yml

@@ -5,7 +5,7 @@ on:
 
 jobs:
   build-debug:
-    runs-on: docker
+    runs-on: [docker, android-app-certs]
     container:
       volumes:
         - android-app-keystore:/keystore

.forgejo/workflows/release.yml

@@ -8,7 +8,7 @@ env:
 
 jobs:
   release:
-    runs-on: docker
+    runs-on: [docker, android-app-certs]
     container:
       volumes:
         - android-app-keystore:/keystore