typings(Collection): use T in accumulator and initialValue when reducing (#3284)
typings(Collection): use T in accumulator and initialValue when reducing (#3284)

This brings some consistency with Array#reduce's typings and to reality.
appellation/discord.js,SpaceEEC/discord.js,SpaceEEC/discord.js,appellation/discord.js,appellation/discord.js,SpaceEEC/discord.js