Fix gRPC dependency

Change-Id: Iddebec60218b555d8ffe39fcabd3daad0b776218
diff --git a/protocols/grpc/api/pom.xml b/protocols/grpc/api/pom.xml
index faae095..3060b3f 100644
--- a/protocols/grpc/api/pom.xml
+++ b/protocols/grpc/api/pom.xml
@@ -46,7 +46,7 @@
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-stub</artifactId>
-           <version>1.3.1</version>
+           <version>${grpccore.version}</version>
        </dependency>
    </dependencies>