Use JDK 11 and remove submodule

Author: manpreet.singh

.github/workflows/gradle.yml

@@ -16,11 +16,11 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-    - name: Set up JDK 1.8
+    - name: Set up JDK 11
       uses: actions/setup-java@v1
       with:
-        java-version: 1.8
+        java-version: 11
     - name: Grant execute permission for gradlew
-      run: chmod +x sseclient/gradlew
+      run: chmod +x gradlew
     - name: Build with Gradle
-      run: ./sseclient/gradlew -p sseclient build test publish
+      run: ./gradlew build test publish