*: fix typos which duplicate a word

Fix typos in code comments which repeat various words.  Most of the
cases are simple in that they repeat a word that usually cannot be
repeated in a grammatically correct sentence.  Just remove the
incorrectly duplicated word in these cases and rewrap text, if needed.

A tricky case is usage of "that that", which is sometimes grammatically
correct.  However, an instance of this in "t7527-builtin-fsmonitor.sh"
doesn't need two words "that", because there is only one daemon being
discussed, so replace the second "that" with "the".

Reword code comment "entries exist on on-disk index" in function
update_one in file cache-tree.c, by replacing incorrect preposition "on"
with "in".

Signed-off-by: Andrei Rybak <rybak.a.v@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/gitprotocol-v2.txt

@@ -665,7 +665,7 @@ headers and their prerequisite relationships, or something else.
 +
 Server operators should feel confident in turning on "bundle-uri" and
 not worry if e.g. their CDN goes down that clones or fetches will run
-into hard failures. Even if the server bundle bundle(s) are
+into hard failures. Even if the server bundle(s) are
 incomplete, or bad in some way the client should still end up with a
 functioning repository, just as if it had chosen not to use this
 protocol extension.