Fix linting errors

[takp]

Changes

There are errors generated by make lint. Some of them are warned by the other PR (Under the Unchanged files with check annotations section).

$ make lint
...
>> verifying modules being imported
>> examining all of the Go files
>> linting all of the Go files GOGC=
server_test.go:151:13: Error return value of `stream.Send` is not checked (errcheck)
	stream.Send(&testpb.PingStreamRequest{})
	           ^
make[1]: *** [lint_module] Error 1
>> verifying modules being imported
>> examining all of the Go files
>> linting all of the Go files GOGC=
interceptors/protovalidate/protovalidate_test.go:127:8: ineffectual assignment to err (ineffassign)
		out, err := client.SendStream(context.Background(), testvalidate.BadStreamRequest)
		     ^
make[1]: *** [lint_module] Error 1
>> verifying modules being imported
>> examining all of the Go files
>> linting all of the Go files GOGC=

Verification

Verified by running make lint again and no errors.

[takp]

@johanbrandhorst Thanks for the review! I've updated them 👍

[johanbrandhorst]

Thanks for your contribution!