Update gRPC, netty and other related dependencies (#35)

## What is the goal of this PR?

We have updated gRPC to 1.29.0. This necessitated netty and other related dependencies to be updated as well.

Author: Ganeshwara Hananda

dependencies/maven/artifacts/io/grpc/BUILD

@@ -37,8 +37,7 @@ java_library(
     runtime_deps = [
         "//dependencies/maven/artifacts/com/google/android:annotations",
         "//dependencies/maven/artifacts/com/google/code/gson:gson",
-        "//dependencies/maven/artifacts/io/opencensus:opencensus-api",
-        "//dependencies/maven/artifacts/io/opencensus:opencensus-contrib-grpc-metrics",
+        "//dependencies/maven/artifacts/com/google/errorprone:error-prone-annotations",
         "//dependencies/maven/artifacts/io/perfmark:perfmark-api",
         ":grpc-api"
     ],

dependencies/maven/artifacts/io/opencensus/BUILD

@@ -4,8 +4,7 @@ java_library(
         "//external:jar/io/perfmark/perfmark-api"
     ],
     runtime_deps = [
-        "//dependencies/maven/artifacts/com/google/code/findbugs:jsr305",
-        "//dependencies/maven/artifacts/com/google/errorprone:error-prone-annotations"
+        "//dependencies/maven/artifacts/com/google/code/findbugs:jsr305"
     ],
     visibility = [
         "//dependencies/maven/artifacts:__subpackages__"