remove: ActiveModel::Serialization#send and ActiveModel::Validations#…

…send (#595)

Passing a Symbol argument to these methods will result in an error.

```
Cannot pass a value of type `::Symbol` as an argument of type `::String`
  ::Symbol <: ::String
    ::Object <: ::String
      ::BasicObject <: ::String(Ruby::ArgumentTypeMismatch)
```

Also, these methods do not exist.

2e17636
It appears to have been added by this commit, but appears to work fine without it.

gems/activemodel/6.0/_test/test.rb

@@ -1,7 +1,10 @@
 class Person
+  include ActiveModel::Model
   include ActiveModel::Validations
   attr_accessor :name, :age, :email
 
   validates :name, presence: true, length: { maximum: 100 }
   validates :email, presence: true, if: -> { age >= 20 }
 end
+
+Person.new.send(:valid?)

gems/activemodel/6.0/patch.rbs

@@ -1,17 +1,3 @@
-module ActiveModel
-  module Serialization
-    # It is necessary to satisfy alias target.
-    # TODO: Define this method to correct place.
-    def `send`: (String name, *untyped args) ?{ (*untyped) -> untyped } -> untyped
-  end
-
-  module Validations
-    # It is necessary to satisfy alias target.
-    # TODO: Define this method to correct place.
-    def `send`: (String name, *untyped args) ?{ (*untyped) -> untyped } -> untyped
-  end
-end
-
 # Remove the fake types for Gem::Version
 # if the real types are available.
 module Gem