cmd/go/testdata/script: fix test script added by CL 334873

CL 334873 added the net/http import to the wrong section in
test_vet.txt. Correct this to fix the longtest builders.

Change-Id: If28409ad1c2ed3bd3a2922fc20d5e534c30fa249
Reviewed-on: https://go-review.googlesource.com/c/go/+/343169
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

src/cmd/go/testdata/script/test_vet.txt

@@ -51,10 +51,7 @@ func Test(t *testing.T) {
 -- p1.go --
 package p
 
-import (
-	"fmt"
-	"net/http"
-)
+import "fmt"
 
 func F() {
 	fmt.Printf("%d") // oops
@@ -62,6 +59,8 @@ func F() {
 -- vetall/p.go --
 package p
 
+import "net/http"
+
 func F() {
 	resp, err := http.Head("example.com")
 	defer resp.Body.Close()