Revert "clutter: add rubyish method convert rule"

This reverts commit 9def9fa88ccbee7999e998989e65886425d31855.

This conversion rule is not suitable for Ruby-GNOME2 naming rule.
Sorry...
clutter: add Clutter::BrightnessContrastEffect::*_full wrapper methods
clutter: add require for wrapping *_full methods in Clutter::BrightnessContrastEffect
clutter: modify copyright year