oidset: stop referring to sha1-array

Ths has been oid_array for some time, though the source only recently
moved from sha1-array.[ch] to oid-array.[ch]. In either case, we should
say "oid-array" here.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

oidset.h

@@ -5,7 +5,7 @@
 #include "khash.h"
 
 /**
- * This API is similar to sha1-array, in that it maintains a set of object ids
+ * This API is similar to oid-array, in that it maintains a set of object ids
  * in a memory-efficient way. The major differences are:
  *
  *   1. It uses a hash, so we can do online duplicate removal, rather than