Fix some rubocop offenses

```
❯ bundle exec rubocop
Inspecting 35 files
..............C....................

Offenses:

lib/rubocop/rspec_rails/description_extractor.rb:60:11: C: [Correctable] Style/MultipleComparison: Avoid comparing a variable with multiple items in a conditional, use Array#include? instead.
          yardoc.superclass.path == RSPEC_RAILS_COP_CLASS_NAME || ...
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
lib/rubocop/rspec_rails/description_extractor.rb:60:39: C: [Correctable] Layout/TrailingWhitespace: Trailing whitespace detected.
          yardoc.superclass.path == RSPEC_RAILS_COP_CLASS_NAME ||
                                      ^
lib/rubocop/rspec_rails/description_extractor.rb:61:15: C: [Correctable] Layout/LineLength: Line is too long. [95/80]
            yardoc.superclass.path == RUBOCOP_COP_CLASS_NAME
              ^^^^^^^^^^^^^^^
lib/rubocop/rspec_rails/description_extractor.rb:60:41: C: [Correctable] Layout/ArrayAlignment: Align the elements of an array literal if they span more than one line.
          yardoc.superclass.path == RSPEC_RAILS_COP_CLASS_NAME ||
                                        ^^^^^^^^^^^^^^^^^^^^^^

35 files inspected, 4 offenses detected, 4 offenses autocorrectable
```

Author: ydah

lib/rubocop/rspec_rails/description_extractor.rb

@@ -57,8 +57,8 @@ def documented_constant
         end
 
         def cop_subclass?
-          yardoc.superclass.path == RSPEC_RAILS_COP_CLASS_NAME ||
-            yardoc.superclass.path == RUBOCOP_COP_CLASS_NAME
+          [RSPEC_RAILS_COP_CLASS_NAME,
+           RUBOCOP_COP_CLASS_NAME].include?(yardoc.superclass.path)
         end
 
         def abstract?