Suppress redundant configuration logging for rubocop-minitest

`rubocop-minitest/config/default.yml` is being output twice:

```console
$ bundle exec rubocop -d lib/rubocop-minitest.rb
For /Users/koic/src/github.com/rubocop/rubocop-minitest: configuration from /Users/koic/src/github.com/rubocop/rubocop-minitest/.rubocop.yml
configuration from /Users/koic/src/github.com/rubocop/rubocop-minitest/config/default.yml
configuration from /Users/koic/.rbenv/versions/3.4-dev/lib/ruby/gems/3.4.0+1/bundler/gems/rubocop-d1123e5aa038/config/internal_affairs.yml
configuration from /Users/koic/.rbenv/versions/3.4-dev/lib/ruby/gems/3.4.0+1/bundler/gems/rubocop-d1123e5aa038/config/internal_affairs.yml
Default configuration from /Users/koic/.rbenv/versions/3.4-dev/lib/ruby/gems/3.4.0+1/bundler/gems/rubocop-d1123e5aa038/config/default.yml
configuration from /Users/koic/.rbenv/versions/3.4-dev/lib/ruby/gems/3.4.0+1/gems/rubocop-performance-1.23.1/config/default.yml
configuration from /Users/koic/.rbenv/versions/3.4-dev/lib/ruby/gems/3.4.0+1/gems/rubocop-performance-1.23.1/config/default.yml
configuration from /Users/koic/src/github.com/rubocop/rubocop-minitest/config/default.yml
configuration from /Users/koic/src/github.com/rubocop/rubocop-minitest/config/default.yml
```

Since it is already logged by `ConfigLoader.load_yaml_configuration`:
https://github.com/rubocop/rubocop/blob/v1.71.2/lib/rubocop/config_loader.rb#L71-L82

The unnecessary code on the caller side will be removed.

lib/rubocop/minitest/inject.rb

@@ -9,9 +9,8 @@ def self.defaults!
         path = CONFIG_DEFAULT.to_s
         hash = ConfigLoader.load_yaml_configuration(path)
         config = Config.new(hash, path).tap(&:make_excludes_absolute)
-        puts "configuration from #{path}" if ConfigLoader.debug?
-        config = ConfigLoader.merge_with_default(config, path)
-        ConfigLoader.instance_variable_set(:@default_configuration, config)
+        new_config = ConfigLoader.merge_with_default(config, path)
+        ConfigLoader.instance_variable_set(:@default_configuration, new_config)
       end
     end
   end