pseudo-merge.h: fix a typo

The comment added in 7252d9a (pseudo-merge: implement support for
finding existing merges, 2024-05-23) misspells 'bitmap' as 'bitamp'.

Correct that so that we no longer have any stray "bitamps" lurking
throughout the tree:

    $ git grep -ci bitamp | wc -l
    0

Noticed-by: Jeff King <[email protected]>
Signed-off-by: Taylor Blau <[email protected]>
Acked-by: Elijah Newren <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: ttaylorr

pseudo-merge.h

@@ -208,7 +208,7 @@ int cascade_pseudo_merges(const struct pseudo_merge_map *pm,
 
 /*
  * Returns a pseudo-merge which contains the exact set of commits
- * listed in the "parents" bitamp, or NULL if none could be found.
+ * listed in the "parents" bitmap, or NULL if none could be found.
  */
 struct pseudo_merge *pseudo_merge_for_parents(const struct pseudo_merge_map *pm,
 					      struct bitmap *parents);