database/sql: fix driverStmt.Close() comment typo

Change-Id: I2256c850e071882b00c362da03abc8b021c1ec2a
Reviewed-on: https://go-review.googlesource.com/126015
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/database/sql/sql.go

@@ -540,7 +540,7 @@ type driverStmt struct {
 	closeErr    error // return value of previous Close call
 }
 
-// Close ensures dirver.Stmt is only closed once any always returns the same
+// Close ensures driver.Stmt is only closed once and always returns the same
 // result.
 func (ds *driverStmt) Close() error {
 	ds.Lock()