go.sum: temporarily delete go.sum file

Change-Id: I050222bc8c111001e5c47c95cd1749c829e4f555
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/166999
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>

go.mod

@@ -1,3 +1,3 @@
 module github.com/golang/protobuf
 
-require github.com/golang/protobuf/v2 v2.0.0-20181127193627-d7e97bc71bcb
+require github.com/golang/protobuf/v2 v2.0.0-20190311214845-9d8c804b555c

go.sum

@@ -1,3 +0,0 @@
-github.com/golang/protobuf v1.2.1-0.20190311202412-6ce2da42b4ff/go.mod h1:5kErVJxM6E04eNoOY5G7ivXy1PbRgsxJrBwZ0obu4lQ=
-github.com/google/go-cmp v0.2.1-0.20181101181452-745b8ec83783 h1:wVZ6laEGf86tNDTpR5mxFyFIclJJiXCxuJhcQKnsOHk=
-github.com/google/go-cmp v0.2.1-0.20181101181452-745b8ec83783/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=