Typofix draft release notes to 1.8.4

Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/RelNotes/1.8.4.txt

@@ -267,7 +267,7 @@ Performance, Internal Implementation, etc.
    been susceptible to lossage of refs under right conditions, which
    has been tightened up.
 
- * We read loose and packed rerferences in two steps, but after
+ * We read loose and packed references in two steps, but after
    deciding to read a loose ref but before actually opening it to read
    it, another process racing with us can unlink it, which would cause
    us to barf.  The codepath has been updated to retry when such a
@@ -379,7 +379,7 @@ details).
 
  * "git apply" parsed patches that add new files, generated by
    programs other than Git, incorrectly.  This is an old breakage in
-   v1.7.11 and will need to be merged down to the maintanance tracks.
+   v1.7.11 and will need to be merged down to the maintenance tracks.
 
  * Older cURL wanted piece of memory we call it with to be stable, but
    we updated the auth material after handing it to a call.