all: change module to google.golang.org/protobuf

Temporarily remove go.mod, since we can't generate an accurate one until
the corresponding v1 change is submitted.

Change-Id: I1e1ad97f2b455e33f61ffaeb8676289795e47e72
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/177000
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
diff --git a/encoding/testprotos/pb2/test.proto b/encoding/testprotos/pb2/test.proto
index db4752e..fe3842b 100644
--- a/encoding/testprotos/pb2/test.proto
+++ b/encoding/testprotos/pb2/test.proto
@@ -6,7 +6,7 @@
 syntax = "proto2";
 
 package pb2;
-option go_package = "github.com/golang/protobuf/v2/encoding/testprotos/pb2";
+option go_package = "google.golang.org/protobuf/encoding/testprotos/pb2";
 
 import "google/protobuf/any.proto";
 import "google/protobuf/empty.proto";