net/rpc: enable TestGobError on Plan 9

This issue has been fixed in CL 31271.

Fixes #8908.

Change-Id: I8015490e2d992e09c664560e42188315e0e0669e
Reviewed-on: https://go-review.googlesource.com/32150
Run-TryBot: David du Colombier <0intro@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/rpc/client_test.go

@@ -8,7 +8,6 @@ import (
 	"errors"
 	"fmt"
 	"net"
-	"runtime"
 	"strings"
 	"testing"
 )
@@ -53,9 +52,6 @@ func (s *S) Recv(nul *struct{}, reply *R) error {
 }
 
 func TestGobError(t *testing.T) {
-	if runtime.GOOS == "plan9" {
-		t.Skip("skipping test; see https://golang.org/issue/8908")
-	}
 	defer func() {
 		err := recover()
 		if err == nil {