Use broken vertical bar as adoc table separator

Follow up #11134 (comment).

This PR uses broken vertical bar as adoc table separator.
It specifies `[separator=¦]` for adoc table to prevent broken regexp format.
https://docs.asciidoctor.org/asciidoc/latest/tables/data-format/#escape-the-cell-separator

adoc generation is updated as follows:

```diff
% bundle exec rake update_cops_documentation
(snip)

% git diff
(snip)

@@ -587,12 +603,13 @@ EOS

 === Configurable attributes

+[separator=¦]
 |===
 | Name | Default value | Configurable values

-| ForbiddenDelimiters
-| `(?-mix:(^|\s)(EO[A-Z]{1}|END)(\s|$))`
-| Array
+¦ ForbiddenDelimiters
+¦ `(?-mix:(^|\s)(EO[A-Z]{1}|END)(\s|$))`
+¦ Array
 |===

 === References
```

lib/rubocop/cops_documentation_generator.rb

@@ -183,9 +183,11 @@ def configurable_values(pars, name)
   # rubocop:enable Metrics/CyclomaticComplexity,Metrics/MethodLength
 
   def to_table(header, content)
-    table = ['|===', "| #{header.join(' | ')}\n\n"].join("\n")
+    # Specify `[separator=¦]` to prevent the regexp `|` is not used as a table separator.
+    # See: https://docs.asciidoctor.org/asciidoc/latest/tables/data-format/#escape-the-cell-separator
+    table = ['[separator=¦]', '|===', "| #{header.join(' | ')}\n\n"].join("\n")
     marked_contents = content.map do |plain_content|
-      plain_content.map { |c| "| #{c}" }.join("\n")
+      plain_content.map { |c| "¦ #{c}" }.join("\n")
     end
     table << marked_contents.join("\n\n")
     table << "\n|===\n"