IcuCollation::$tailoringFirstLetters: letter removal rules for Finnish

Four non-ASCII letters - Ǥ, Ŋ, Ŧ, Ʒ - are sorted the same as their
unaccented base ASCII versions - G, N, T, Z - causing unexpected
output on category pages.

Bug: 46330
Change-Id: I976dedfdc651fcc96a2291934924aa40b27f4c2f
Merge "IcuCollation::$tailoringFirstLetters: letter removal rules for Finnish" into wmf/1.21wmf12