fix quote (#3359)

Author: craigbox

mesh/v1alpha1/config.pb.go

@@ -1289,7 +1289,7 @@ message MeshConfig {
       google.protobuf.Duration timeout = 1;
 
       // Optional. Additional metadata to include in streams initiated to the GrpcService. This can be used for
-      // scenarios in which additional ad hoc authorization headers (e.g. “x-foo-bar: baz-key“) are to
+      // scenarios in which additional ad hoc authorization headers (e.g. "x-foo-bar: baz-key") are to
       // be injected.
       repeated HttpHeader initial_metadata = 2;
     }