deps: override grpc-gcp version to 1.9.0 to fix NoSuchMethodError

Author: rahul2393

pom.xml

@@ -72,6 +72,12 @@
         <type>pom</type>
         <scope>import</scope>
       </dependency>
+      <!-- Override grpc-gcp version from shared-dependencies BOM to match google-cloud-spanner requirements -->
+      <dependency>
+        <groupId>com.google.cloud</groupId>
+        <artifactId>grpc-gcp</artifactId>
+        <version>1.9.0</version>
+      </dependency>
       <dependency>
         <groupId>io.opencensus</groupId>
         <artifactId>opencensus-api</artifactId>