chore: skip clirr 7012 exceptions with grpc admin package #3222 (#3305)

Author: rahul2393

grpc-google-cloud-spanner-admin-instance-v1/clirr-ignored-differences.xml

@@ -3,7 +3,7 @@
 <differences>
   <difference>
     <differenceType>7012</differenceType>
-    <className>com/google/spanner/admin/instance/v1/InstanceAdminGrpc$AsyncService</className>
-    <method>*InstancePartition*(*)</method>
+    <className>com/google/spanner/admin/instance/v1/*</className>
+    <method>*</method>
   </difference>
 </differences>