vendor: Update github.com/gogo/protobuf, keeping all files

gvt fetch -a, because we need the protobuf files etc for regeneration

vendor/github.com/gogo/protobuf/test/issue260/issue260.proto

@@ -0,0 +1,36 @@
+syntax = "proto3";
+
+package issue260;
+
+import "github.com/gogo/protobuf/gogoproto/gogo.proto";
+import "google/protobuf/timestamp.proto";
+
+option (gogoproto.testgen_all) = true;
+option (gogoproto.populate_all) = true;
+option (gogoproto.benchgen_all) = true;
+option (gogoproto.unmarshaler_all) = true;
+option (gogoproto.marshaler_all) = true;
+option (gogoproto.sizer_all) = true;
+option (gogoproto.equal_all) = true;
+option (gogoproto.verbose_equal_all) = true;
+option (gogoproto.unsafe_marshaler_all) = false;
+option (gogoproto.unsafe_unmarshaler_all) = false;
+
+message Dropped {
+    option (gogoproto.typedecl) = false;
+    string name = 1;
+    int32 age = 2;
+}
+
+message DroppedWithoutGetters {
+    option (gogoproto.typedecl) = false;
+    option (gogoproto.goproto_getters) = false;
+    int64 height = 1;
+    int64 width = 2;
+    google.protobuf.Timestamp timestamp = 3 [(gogoproto.stdtime) = true, (gogoproto.nullable) = false];
+}
+
+message Kept {
+    string name = 1;
+    int32 age = 2;
+}