deps: update gRPC (#2024)

* deps: update protobuf and gRPC

@rghetia

* deps: revert protobuf

* add release notes

Author: elharo

CHANGELOG.md

@@ -1,5 +1,11 @@
 ## Unreleased
 
+
+## 0.26.0 - 2020-04
+- gRPC metrics collection now requires the 
+  [`io.grpc:grpc-census`](https://github.com/grpc/grpc-java/releases/tag/v1.27.0)
+  artifact in addition to this module. 
+
 ## 0.25.0 - 2020-02-12
 - Add an experimental artifact `opencensus-contrib-observability-ready-util`, that allows users to
 use OpenCensus easily.

build.gradle

@@ -161,7 +161,7 @@ subprojects {
         findBugsAnnotationsVersion = '3.0.1'
         findBugsJsr305Version = '3.0.2'
         errorProneVersion = '2.3.2'
-        grpcVersion = '1.25.0'
+        grpcVersion = '1.27.2'
         guavaVersion = '28.2-android'
         googleAuthVersion = '0.20.0'
         googleCloudBetaVersion = '0.100.0-beta'