Fix the issues reported by phpcs

Finding the above errors. I'll work on solving them.

I have fixed all of the above except for the dependency injection. Please review the MR.
Thanks.

Hi sidharth_soman, I have made some updates to the code and fixed the issue related to the

\Drupal calls should be avoided in classes, use dependency injection instead

Please review the patch.

   public function applies(RouteMatchInterface $route_match): bool {
     return $route_match->getRouteName() === 'system.admin_content';
+
   }

An empty line is not necessary after a return line.

+  /**
+   * Constructs a Help object.
+   *
+   * @param \Drupal\contextual_help\HelpManager $help_manager
+   *   The help manager service.

The short description is missing the class namespace.

+  /**
+   * The RedirectDestinationInterface service.
+   *
+   * @var \Drupal\Core\Routing\RedirectDestinationInterface

That is not the service name, but the class name. The service could be probably be described as The redirect service. or The redirect destination service. as another comment describes it. I would rather use the description used on Drupal::destination() in both the cases: The redirect destination helper.

+   * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
+   *   Cache backend instance to use.

That description is missing an article.

   /**
    * Get a link to the help plugin text by plugin definition.
    *
-   * @param $definition
+   * @param array $definition
    *   The plugin definition.

Since that comment is changed, the verb used on the short description should be changed to use the third person singular (which is an on-topic change since this issue is about coding standards).

I have created the MR !2 with the required changes please check

Addressed the comment on MR. Please review.

i have done required changes that were mention in MR !2 comments

@kalash-j there are still some phpcs issue left.