Fix link to documentation about configuration in .rubocop.yml

The link in the generated .rubocop.yml is outdated.

- I updated it.
- I updated the spec that controls the content of .rubocop.yml.
- I also updated the link to the same page where it appears in the docs.

docs/modules/ROOT/pages/usage/basic_usage.adoc

@@ -167,7 +167,7 @@ $ rubocop -h
 | Inspect files in order of modification time and stops after first file with offenses.
 
 | `--fail-level`
-| Minimum link:configuration.md#severity[severity] for exit with error code. Full severity name or upper case initial can be given. Normally, auto-corrected offenses are ignored. Use `A` or `autocorrect` if you'd like them to trigger failure.
+| Minimum xref:configuration.adoc#severity[severity] for exit with error code. Full severity name or upper case initial can be given. Normally, auto-corrected offenses are ignored. Use `A` or `autocorrect` if you'd like them to trigger failure.
 
 | `--force-exclusion`
 | Force excluding files specified in the configuration `Exclude` even if they are explicitly passed as arguments.

lib/rubocop/cli/command/init_dotfile.rb

@@ -27,7 +27,7 @@ def run
               # RuboCop will start looking for the configuration file in the directory
               # where the inspected file is and continue its way up to the root directory.
               #
-              # See https://github.com/rubocop-hq/rubocop/blob/master/manual/configuration.md
+              # See https://docs.rubocop.org/rubocop/configuration
             DESC
 
             File.open(DOTFILE, 'w') do |f|

spec/rubocop/cli_spec.rb

@@ -243,7 +243,7 @@ def and_with_args
             # RuboCop will start looking for the configuration file in the directory
             # where the inspected file is and continue its way up to the root directory.
             #
-            # See https://github.com/rubocop-hq/rubocop/blob/master/manual/configuration.md
+            # See https://docs.rubocop.org/rubocop/configuration
           YAML
         end
       end