Move arity check filters to opal bugs

Author: meh

spec/opal/filters/bugs/arity_check.rb

@@ -1,3 +1,7 @@
 opal_filter "Opal bugs" do
   fails "Array#join raises a NoMethodError if an element does not respond to #to_str, #to_ary, or #to_s"
+
+  # arity checking bugs
+  fails "Array#shift passed a number n as an argument raises an ArgumentError if more arguments are passed"
+  fails "Array#pop passed a number n as an argument raises an ArgumentError if more arguments are passed"
 end