remote-mediawiki doc: don't hardcode Debian PHP versions

Change the hardcoded version 5 PHP versions to the version-agnostic
packages. Currently Debian stable's version is 7.3, and there's a
php7.3, php7.3-cli etc. package available (but no php5-*).

The corresponding version-less package is a dependency package which
depends on whatever the current stable version is. By not hardcoding
the version these instructions won't be out of date when the next
Debian/Ubuntu release happens.

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

contrib/mw-to-git/t/README

@@ -14,11 +14,11 @@ install the following packages (Debian/Ubuntu names, may need to be
 adapted for another distribution):
 
 * lighttpd
-* php5
+* php
-* php5-cgi
+* php-cgi
-* php5-cli
+* php-cli
-* php5-curl
+* php-curl
-* php5-sqlite
+* php-sqlite
 
 Principles and Technical Choices
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