go.mod: temporarily delete go.mod file

Change-Id: I23933890226513318f13094009167aa7922361b4
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/166885
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>

go.mod

@@ -1,6 +0,0 @@
-module github.com/golang/protobuf/v2
-
-require (
-	github.com/golang/protobuf v1.2.1-0.20190311214837-379b5a7ff78a
-	github.com/google/go-cmp v0.2.1-0.20181101181452-745b8ec83783
-)