Fix an error for Style/SingleLineMethods

This PR fixes the following error for `Style/SingleLineMethods`.

```console
% cat  example.rb
def some_method; 42 end

% bundle exec rubocop --only Style/SingleLineMethods -d

(snip)

undefined method `arguments' for s(:int, 42):RuboCop::AST::IntNode
Did you mean?  argument?
/Users/koic/src/github.com/rubocop/rubocop/lib/rubocop/cop/style/single_line_methods.rb:118:in `method_body_source'
```

This is a regression of rubocop#9704.

lib/rubocop/cop/style/single_line_methods.rb

@@ -115,7 +115,7 @@ def move_comment(node, corrector)
         end
 
         def method_body_source(method_body)
-          if method_body.arguments.empty? || method_body.parenthesized?
+          if !method_body.send_type? || method_body.arguments.empty? || method_body.parenthesized?
             method_body.source
           else
             arguments_source = method_body.arguments.map(&:source).join(', ')

spec/rubocop/cop/style/single_line_methods_spec.rb

@@ -187,6 +187,12 @@ def some_method(a, b, c) = body
         RUBY
       end
 
+      it 'corrects to an endless method definition when method body is a literal' do
+        expect_correction(<<~RUBY.strip, source: 'def some_method; 42 end')
+          def some_method() = 42
+        RUBY
+      end
+
       it 'corrects to an endless method definition when single line method call with parentheses' do
         expect_correction(<<~RUBY.strip, source: 'def index() head(:ok) end')
           def index() = head(:ok)