go/internal/gcimporter: simplify defer

Directly use rc.Close instead of wrapping it with a closure.

Change-Id: I3dc1c21ccbfe031c230b035126d5ea3bc62055c3
Reviewed-on: https://go-review.googlesource.com/99716
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/go/internal/gcimporter/gcimporter.go

@@ -133,9 +133,7 @@ func Import(packages map[string]*types.Package, path, srcDir string, lookup func
 		}()
 		rc = f
 	}
-	defer func() {
-		rc.Close()
-	}()
+	defer rc.Close()
 
 	var hdr string
 	buf := bufio.NewReader(rc)