testing/prototest: fix suggestion for field name
testing/prototest: fix suggestion for field name

We should use TextName instead of Name,
since it is the name that actually appears in the .proto file.

Change-Id: Ie526b200d18b0994d93dbb347c266fa5c50cddfe
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/241658
Reviewed-by: Herbie Ong <86f376bf42b6daa37c768c730acd318ab6855de4@google.com>

protocolbuffers/protobuf-go,protocolbuffers/protobuf-go