Use FQCN for SetRegistry/SetCollector (TYPO3-Documentation#4831)

* [TASK] Use FQCN for SetRegistry/SetCollector

Co-authored-by: Lina Wolf <48202465+linawolf@users.noreply.github.com>

Documentation/ApiOverview/SiteHandling/SiteSets.rst

@@ -392,12 +392,13 @@ already been validated, converted and, if not set, the default value is used.
 SetRegistry
 -----------
 
-The `SetRegistry` retrieves the site sets found in an ordered sequence, as
+The :php:`\TYPO3\CMS\Core\Site\Set\SetRegistry` retrieves the site sets found in an ordered sequence, as
 defined by `dependencies` in `config.yaml`. Please preferably use the site
 object to access the required data. However, if you need to query one or more
-site set definitions in order as defined by dependencies, then `SetRegistry`
+site set definitions in order as defined by dependencies, then
+:php-short:`\TYPO3\CMS\Core\Site\Set\SetRegistry`
 is the right place to go. To read all site set definitions, please
-use `SetCollector`.
+use :php:`TYPO3\CMS\Core\Site\Set\SetCollector`.
 
 ..  _site-sets-php-api-setregistry-getsets:
 
@@ -438,7 +439,7 @@ SetCollector
 ~~~~~~~~~~~~
 
 TYPO3 comes with a new `ServiceProvider`, which goes through all extensions
-with the first instantiation of the `SetCollector` and reads all site set
+with the first instantiation of the :php-short:`\TYPO3\CMS\Core\Site\Set\SetCollector` and reads all site set
 definitions found.
 
 ..  code-block:: php
@@ -450,8 +451,8 @@ definitions found.
 
 However, this is not the official way to access the site set definitions and
 their dependencies. Please access the configuration via the site object.
-Alternatively, you can also use the `SetRegistry`, as only this manages the
+Alternatively, you can also use the :php-short:`\TYPO3\CMS\Core\Site\Set\SetRegistry`, as only this manages the
 site sets in the order declared by the dependency specification.
 
-Only use the `SetCollector` if you need to read all site set definitions.
+Only use the :php-short:`\TYPO3\CMS\Core\Site\Set\SetCollector` if you need to read all site set definitions.
 Dependencies are not taken into account here.