Of course, any changes to a theme will reside within a WordPress child theme.
Broadly speaking, this should do it:
$post_title = get_the_title();
$post_title_output = explode( " ", $post_title );
array_splice( $post_title_output, -2 );
echo implode( " ", $post_title_output );
4
solved It is Possible to remove last words of current post title and echo the result?