Update coder to 8.3.7

Problem/Motivation

Update drupal/coder to the latest version.

• Includes PHP 7.4 support
• Bugfixes
• #2958175: Add rule to prevent direct usage of $_GET, $_POST, $_REQUEST and $_FILES in Drupal 8

Proposed resolution

Fix failing coding standards. Note DateTimePlus contains some non-standard documentation that doesn't work. See $settings documentation on https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Component%21Date...

    * @param array $settings
    *   @see __construct()

The @see does not work at all - and doesn't work in PHPStorm either. Fortunately there are other methods that already have

   * @param array $settings
   *   (optional) A keyed array for settings, suitable for passing on to
   *   __construct().

so we can copy that.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet