encoding: cleanup some tests

Change-Id: I07b8cd5e9b71fea6a162ca423186b4df7fd49355
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/185458
Reviewed-by: Herbie Ong <herbie@google.com>
diff --git a/encoding/prototext/decode_test.go b/encoding/prototext/decode_test.go
index 799de2e..d32c01e 100644
--- a/encoding/prototext/decode_test.go
+++ b/encoding/prototext/decode_test.go
@@ -352,8 +352,8 @@
 opt_nested_enum: -101
 `,
 		wantMessage: &pb2.Enums{
-			OptEnum:       pb2Enum(101),
-			OptNestedEnum: pb2Enums_NestedEnum(-101),
+			OptEnum:       pb2.Enum(101).Enum(),
+			OptNestedEnum: pb2.Enums_NestedEnum(-101).Enum(),
 		},
 	}, {
 		desc:         "proto2 enum set to invalid named",