deps: update core dependencies

Author: Renovate Bot

pom.xml

@@ -66,8 +66,8 @@
     <google.core.version>1.91.3</google.core.version>
     <google.api-common.version>1.8.1</google.api-common.version>
     <google.common-protos.version>1.17.0</google.common-protos.version>
-    <gax.version>1.51.0</gax.version>
-    <grpc.version>1.25.0</grpc.version>
+    <gax.version>1.52.0</gax.version>
+    <grpc.version>1.26.0</grpc.version>
     <protobuf.version>3.11.1</protobuf.version>
     <junit.version>4.12</junit.version>
     <guava.version>28.1-android</guava.version>