Improve specs for Symbol#to_proc
Improve specs for Symbol#to_proc

* dry-initializer relies on the arity being -1, see
  https://github.com/oracle/truffleruby/issues/1462
  https://github.com/dry-rb/dry-initializer/issues/52

eregon/rubyspec,nobu/rubyspec,ruby/spec,nobu/rubyspec,ruby/spec,nobu/rubyspec,eregon/rubyspec,eregon/rubyspec,ruby/spec,ruby/rubyspec,ruby/rubyspec