refs.c: lock_ref_sha1_basic is used for all refs

lock_ref_sha1_basic is used to lock refs that sit directly in the .git
dir such as HEAD and MERGE_HEAD in addition to the more ordinary refs
under "refs/".  Remove the note claiming otherwise.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -2134,7 +2134,7 @@ int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 }
 
 /*
- * Locks a "refs/" ref returning the lock on success and NULL on failure.
+ * Locks a ref returning the lock on success and NULL on failure.
  * On failure errno is set to something meaningful.
  */
 static struct ref_lock *lock_ref_sha1_basic(const char *refname,