Remove "raise vs E2MM#Raise" benchmark from repository

It's nice that someone found that this library is so slow but I think most Ruby devs don't know that e2mmap even exists (actually I learned about this library from this repo). IMHO it would be better to not tell other developers that it exists. I even grepped all gems from ~/.rbenv/ (more that 2000 gems) and only rdoc & yard gems use it (actually they include file [ruby_lex.rb](https://github.com/ruby/ruby/blob/trunk/lib/rdoc/ruby_lex.rb)). All other benchmarks are more or less used in a real code but this one is completely impractical.