INSTALL: don't mention the "curl" executable at all

In 1d53f90ed9 (The "curl" executable is no longer required,
2008-06-15) the wording for requiring curl(1) was changed to the
current "you might also want...".

Mentioning the "curl" executable at all is just confusing, someone
building git might want to use it to debug things, but they might also
just use wget(1) or some other http client. The "curl" executable has
the advantage that you might be able to e.g. reproduce a bug in git's
usage of libcurl with it, but anyone going to those extents is
unlikely to be aided by this note in INSTALL.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

INSTALL

@@ -139,8 +139,7 @@ Issues of note:
 	  (PPC_SHA1).
 
 	- "libcurl" library is used by git-http-fetch, git-fetch, and, if
-	  the curl version >= 7.34.0, for git-imap-send.  You might also
-	  want the "curl" executable for debugging purposes. If you do not
+	  the curl version >= 7.34.0, for git-imap-send. If you do not
 	  use http:// or https:// repositories, and do not want to put
 	  patches into an IMAP mailbox, you do not have to have them
 	  (use NO_CURL).