Remove deprecated method Kernel#=~

Author: patricklinpl

spec/tags/core/kernel/match_tags.txt

@@ -181,13 +181,8 @@ def `(str) #`
   end
   module_function :` # `
 
-  def =~(other)
-    warn "deprecated Object#=~ is called on #{Primitive.class(self)}; it always returns nil", uplevel: 1 if $VERBOSE
-    nil
-  end
-
   def !~(other)
-    r = self =~ other ? false : true
+    r = self.respond_to?(:=~) ? !(self =~ other) : true
     Primitive.regexp_last_match_set(Primitive.caller_special_variables, $~)
     r
   end