deps: update dependency io.grpc:grpc-bom to v1.24.0 (#8)

Author: renovate-bot

pom.xml

@@ -66,7 +66,7 @@
     <google.api-common.version>1.8.1</google.api-common.version>
     <google.common-protos.version>1.16.0</google.common-protos.version>
     <gax.version>1.48.1</gax.version>
-    <grpc.version>1.23.0</grpc.version>
+    <grpc.version>1.24.0</grpc.version>
     <protobuf.version>3.10.0</protobuf.version>
     <junit.version>4.12</junit.version>
     <guava.version>28.0-android</guava.version>