Removing Travis and GCB integrations (#347)

* Removing Travis and GCB integrations

* Updated CI badge

Author: hiranya911

.github/workflows/ci.yml

@@ -1,12 +1,10 @@
-name: Java Continuous Integration
+name: Continuous Integration
 
 on: [push, pull_request]
 
 jobs:
   build:
-
     runs-on: ubuntu-latest
-
     steps:
     - uses: actions/checkout@v1
     - name: Set up JDK 1.7

.travis.yml

@@ -1,4 +1,4 @@
-[![Build Status](https://travis-ci.org/firebase/firebase-admin-java.svg?branch=master)](https://travis-ci.org/firebase/firebase-admin-java)
+[![Build Status](https://github.com/firebase/firebase-admin-java/workflows/Continuous%20Integration/badge.svg)](https://github.com/firebase/firebase-admin-java/actions)
 [![Maven Central](https://maven-badges.herokuapp.com/maven-central/com.google.firebase/firebase-admin/badge.svg)](https://maven-badges.herokuapp.com/maven-central/com.google.firebase/firebase-admin)
 [![Javadoc](https://javadoc-badge.appspot.com/com.google.firebase/firebase-admin.svg)](https://firebase.google.com/docs/reference/admin/java/reference/packages)