deps: explicitly define grpc-gcp version

Author: olavloite

pom.xml

@@ -65,6 +65,11 @@
         <type>pom</type>
         <scope>import</scope>
       </dependency>
+      <dependency>
+        <groupId>com.google.cloud</groupId>
+        <artifactId>grpc-gcp</artifactId>
+        <version>1.9.0</version>
+      </dependency>
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-shared-dependencies</artifactId>