Remove redundant "bundler/setup"

Having "bundler/setup" in spec_helper doesn't make
much sense. On the other hand, it becomes a problem
for downstream as they constantly have to keep patching
this from all the libraries.

Signed-off-by: Utkarsh Gupta <utkarsh@debian.org>

bundler/lib/bundler/templates/newgem/spec/spec_helper.rb.tt

@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require "bundler/setup"
 require "<%= config[:namespaced_path] %>"
 
 RSpec.configure do |config|