Fix SpecialPageTest

1) Only execute Translate special pages, not all special pages. Was broken
when composer support was added.
2) Return early on Special:SupportedLanguages
3) Fix undefined variable in Special:PageTranslationDeletePage

Bug: 67036
Change-Id: I6e84fce1443d89ad739d5312354e15efc7ffdd58
Merge "Fix SpecialPageTest"