zshrc: use history-beginning-search-{forward,backward}-end instead of the version...

zshrc: use history-beginning-search-{forward,backward}-end instead of the version without "-end".

This further improves Bernhard's history-beginning-search with
PageUp/PageDown feature as it moves the cursor at the end
of the line then.

Thanks: Frank Terbeck <ft@grml.org>