Remove the code that in hook_install() shows the link to the module settings page

Problem/Motivation

The hook_install() implementation shows a link to the module settings page, but that is not necessary, since that link is already provided in the page showing the list of all the modules.

Proposed resolution

Remove the following code from multiple_email_install().

  $link_text_parts = [
    new TranslatableMarkup('Administer'),
    new TranslatableMarkup('Configuration'),
    new TranslatableMarkup('People'),
    new TranslatableMarkup('Multiple email'),
  ];
  $link_text = implode(' > ', $link_text_parts);

  $link = Link::createFromRoute($link_text, 'multiple_email.admin.settings');

  $message = new TranslatableMarkup('Multiple email settings are available under @link', [
    '@link' => $link->toString(),
  ]);

  Drupal::messenger()->addMessage($message);

Code showing a link should not try to build its breadcrumb; that is not how links are shown in Drupal.