Fix the errors reported by PHPCS

Problem/Motivation

While checking with PHPCS, able to see some errors. Needs to fix them

Steps to reproduce

Run PHPCS can show us errors/suggestions

Proposed resolution

Check the errors/suggestions and need fix for them
FILE: /var/www/html/web/modules/contrib/find_external_links-3379871/src/Form/ConfigurationForm.php
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FOUND 0 ERRORS AND 3 WARNINGS AFFECTING 3 LINES
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158 | WARNING | \Drupal calls should be avoided in classes, use dependency injection instead
238 | WARNING | \Drupal calls should be avoided in classes, use dependency injection instead
242 | WARNING | \Drupal calls should be avoided in classes, use dependency injection instead
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