Fix encoding method of RuboCop::MagicComment::SimpleComment

�$B!.�(BLint/OrderedMagicComments�$B!.�(B cop extracts codes including "encoding:" that is not comment.
e.g. `CSV.generate(encoding: Encoding::UTF_8) do |csv|`

I think that is solved by adding the condition of "# " before "encoding:".

CHANGELOG.md

@@ -9,6 +9,7 @@
 * [#5633](https://github.com/bbatsov/rubocop/pull/5633): Fix broken `--fail-fast`. ([@mmyoji][])
 * [#5630](https://github.com/bbatsov/rubocop/issues/5630): Fix false positive for `Style/FormatStringToken` when using placeholder arguments in `format` method. ([@koic][])
 * [#5651](https://github.com/bbatsov/rubocop/pull/5651): Fix NoMethodError when specified config file that does not exist. ([@onk][])
+* [#5647](https://github.com/bbatsov/rubocop/pull/5647): Fix encoding method of RuboCop::MagicComment::SimpleComment. ([@htwroclau][])
 
 ### Changes
 
@@ -3242,3 +3243,4 @@
 [@colorbox]: https://github.com/colorbox
 [@mmyoji]: https://github.com/mmyoji
 [@unused]: https://github.com/unused
+[@htwroclau]: https://github.com/htwroclau

lib/rubocop/magic_comment.rb

@@ -190,7 +190,7 @@ def frozen_string_literal; end
     class SimpleComment < MagicComment
       # Match `encoding` or `coding`
       def encoding
-        extract(/\b(?:en)?coding: (#{TOKEN})/i)
+        extract(/\#* \b(?:en)?coding: (#{TOKEN})/i)
       end
 
       private

spec/rubocop/magic_comment_spec.rb

@@ -84,6 +84,11 @@
                    encoding: 'ascii-8bit',
                    frozen_string_literal: nil
 
+  include_examples 'magic comment',
+                   ' CSV.generate(encoding: Encoding::UTF_8) do |csv|',
+                   encoding: nil,
+                   frozen_string_literal: nil
+
   include_examples(
     'magic comment',
     '# -*- encoding: ASCII-8BIT; frozen_string_literal: true -*-',