minor #49239 Fix some typos (javiereguiluz)

This PR was merged into the 5.4 branch.

Discussion
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Fix some typos

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

Commits
-------

bb62f1718a Fix some typos

Resource/ClassExistenceResource.php

@@ -32,7 +32,7 @@ class ClassExistenceResource implements SelfCheckingResourceInterface
 
     /**
      * @param string    $resource The fully-qualified class name
-     * @param bool|null $exists   Boolean when the existency check has already been done
+     * @param bool|null $exists   Boolean when the existence check has already been done
      */
     public function __construct(string $resource, bool $exists = null)
     {