Build: Upgrade gRPC version. (#2001)

Author: twixthehero

build.gradle

@@ -161,7 +161,7 @@ subprojects {
         findBugsAnnotationsVersion = '3.0.1'
         findBugsJsr305Version = '3.0.2'
         errorProneVersion = '2.3.2'
-        grpcVersion = '1.22.1'
+        grpcVersion = '1.25.0'
         guavaVersion = '26.0-android'
         googleAuthVersion = '0.16.2'
         googleCloudBetaVersion = '0.100.0-beta'