Update links to the modules and themes search pages at Drupal.org

Problem/Motivation

The links to the search pages for modules and for themes have changed:

Old: https://www.drupal.org/project/themes →
New: https://www.drupal.org/project/project_theme →

Old: https://www.drupal.org/project/modules →
New: https://www.drupal.org/project/project_module →

Steps to reproduce

Visit the following pages and notice that the old links are shown:

- admin/help: In the "Getting Started" section.
- admin/help/field: In the "Uses" section.
- admin/help/system: In the "Uses" section

Proposed resolution

Update the links.

Remaining tasks

Create Merge Request

User interface changes

Links in the administrative help sections are updated to reflect new path aliases to the modules and themes search pages on Drupal.org.

Introduced terminology

none

API changes

none

Data model changes

none

Release notes snippet

Links in the administrative help sections have been updated to reflect new path aliases to the modules and themes search pages on Drupal.org.