git-rebase.txt: fix description list separator

We don't give a "::" for the list separator, but just a single ":". This
ends up rendering literally, "--apply: Use applying strategies ...". As
a follow-on error, the list continuation, "+", also ends up rendering
literally (because we don't have a list).

This was introduced in 52eb738d6b ("rebase: add an --am option",
2020-02-15) and survived the rename in 10cdb9f38a ("rebase: rename the
two primary rebase backends", 2020-02-15).

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index f7a6033..9acea05 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -258,7 +258,7 @@
 	original branch. The index and working tree are also left
 	unchanged as a result.
 
---apply:
+--apply::
 	Use applying strategies to rebase (calling `git-am`
 	internally).  This option may become a no-op in the future
 	once the merge backend handles everything the apply one does.