phpcs-HEAD now ignores i18n files

20c1073 / https://gerrit.wikimedia.org/r/#/c/58638/ made 'phpcs' to
ignore the i18n files but forgot to do the same for 'phpcs-HEAD'.

bug: 48420
Change-Id: Ia3cbaddf698eac558d2390a4be5d8c0817bf6317