Doc: Add missing \title to GRPC client guide example

Pick-to: 6.8 6.9
Change-Id: I8bf7f2e5b578b58f67816c02fd4c2b2f00aba798
Reviewed-by: Dennis Oberst <dennis.oberst@qt.io>

examples/grpc/clientguide/doc/src/clientguide.qdoc

@@ -3,6 +3,7 @@
 
 /*!
     \example clientguide
+    \title Qt GRPC Client Guide
     \ingroup qtgrpc-examples
     \examplecategory {Networking}
     \meta tag {network,protobuf,grpc,serialization,overview}