Add timeout to workflows

The default timeout is 6 hours, which is unnecessarily long. We should
stop tests if it doesn't finish in 10~15 mins to see what happens.

Author: st0012

.github/workflows/protocol.yml

@@ -17,6 +17,7 @@ jobs:
   test:
 
     runs-on: ubuntu-latest
+    timeout-minutes: 10
     strategy:
       matrix:
         ruby-version: ['2.6', '2.7', '3.0', '3.1', 'head', 'debug']

.github/workflows/ruby.yml

@@ -17,6 +17,7 @@ jobs:
   test:
 
     runs-on: ubuntu-latest
+    timeout-minutes: 15
     strategy:
       matrix:
         ruby-version: ['2.6', '2.7', '3.0', '3.1', 'head', 'debug']