gitweb tests: change confusing "skip_all" phrasing

Change the phrasing so that instead of saying that the CGI module is
unusable, we say that it's not available.

This came up on the git mailing list in
<4b34e3a0-3da7-d821-2a7f-9a420ac1d3f6@gmail.com> from Jakub Narębski.

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

t/gitweb-lib.sh

@@ -110,7 +110,7 @@ perl -MEncode -e '$e="";decode_utf8($e, Encode::FB_CROAK)' >/dev/null 2>&1 || {
 }
 
 perl -MCGI -MCGI::Util -MCGI::Carp -e 0 >/dev/null 2>&1 || {
-	skip_all='skipping gitweb tests, CGI module unusable'
+	skip_all='skipping gitweb tests, CGI & CGI::Util & CGI::Carp modules not available'
 	test_done
 }