Add "java-version: 11" to verify.yml

The "11" is the version which is used on AtCoder.

Author: kmyk

.github/workflows/verify.yml

@@ -23,6 +23,8 @@ jobs:
     # required only if you want to verify Java code
     - name: Install dependencies (Java)
       uses: actions/setup-java@v1
+      with:
+        java-version: 11
 
     # required only if you want to verify C# script files
     - uses: actions/setup-dotnet@v1