minor #48007 Fix Typos In Comments 5.4+ (PhilETaylor)

This PR was merged into the 5.4 branch.

Discussion
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Fix Typos In Comments 5.4+

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

Non complicated, uncontroversial typo fixes in comments only (no PHP code changes) across the codebase in the 5.4 branch while sat on the sofa watching TV.

Commits
-------

792c221406 Typos In Comments

Author: derrabus

FormFieldRegistry.php

@@ -47,7 +47,7 @@ public function add(FormField $field)
     }
 
     /**
-     * Removes a field based on the fully qualifed name and its children from the registry.
+     * Removes a field based on the fully qualified name and its children from the registry.
      */
     public function remove(string $name)
     {
@@ -64,7 +64,7 @@ public function remove(string $name)
     }
 
     /**
-     * Returns the value of the field based on the fully qualifed name and its children.
+     * Returns the value of the field based on the fully qualified name and its children.
      *
      * @return FormField|FormField[]|FormField[][]
      *