Issue #3189101 by paulocs, ranjith_kumar_k_u: Update documented links from form.api.php

(cherry picked from commit 87aba80b166fd4a8f0abf9527686417455f21f44)

core/lib/Drupal/Core/Form/form.api.php

@@ -165,7 +165,7 @@ function hook_ajax_render_alter(array &$data) {
  * $form_state->getFormObject()->getEntity().
  *
  * Implementations are responsible for adding cache contexts/tags/max-age as
- * needed. See https://www.drupal.org/developing/api/8/cache.
+ * needed. See https://www.drupal.org/docs/8/api/cache-api/cache-api.
  *
  * In addition to hook_form_alter(), which is called for all forms, there are
  * two more specific form hooks available. The first,
@@ -216,7 +216,7 @@ function hook_form_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_stat
  * Provide a form-specific alteration instead of the global hook_form_alter().
  *
  * Implementations are responsible for adding cache contexts/tags/max-age as
- * needed. See https://www.drupal.org/developing/api/8/cache.
+ * needed. See https://www.drupal.org/docs/8/api/cache-api/cache-api.
  *
  * Modules can implement hook_form_FORM_ID_alter() to modify a specific form,
  * rather than implementing hook_form_alter() and checking the form ID, or
@@ -259,7 +259,7 @@ function hook_form_FORM_ID_alter(&$form, \Drupal\Core\Form\FormStateInterface $f
  * Provide a form-specific alteration for shared ('base') forms.
  *
  * Implementations are responsible for adding cache contexts/tags/max-age as
- * needed. See https://www.drupal.org/developing/api/8/cache.
+ * needed. See https://www.drupal.org/docs/8/api/cache-api/cache-api.
  *
  * By default, when \Drupal::formBuilder()->getForm() is called, Drupal looks
  * for a function with the same name as the form ID, and uses that function to