minor #33264 [4.4] Add return types on internal|final|private methods (bis) (nicolas-grekas)

This PR was merged into the 4.4 branch.

Discussion
----------

[4.4] Add return types on internal|final|private methods (bis)

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Found while working on #33259

`: self` is used for final methods only. I'd have preferred using `: object` but that's not possible on PHP 7.1

Commits
-------

23faee406f [4.4] Add return types on internal|final|private methods (bis)

Author: nicolas-grekas

Loader/Configurator/CollectionConfigurator.php

@@ -60,7 +60,7 @@ final public function collection($name = ''): self
      *
      * @return $this
      */
-    final public function prefix($prefix)
+    final public function prefix($prefix): self
     {
         if (\is_array($prefix)) {
             if (null === $this->parentPrefixes) {

Loader/Configurator/ImportConfigurator.php

@@ -41,7 +41,7 @@ public function __destruct()
      *
      * @return $this
      */
-    final public function prefix($prefix, bool $trailingSlashOnRoot = true)
+    final public function prefix($prefix, bool $trailingSlashOnRoot = true): self
     {
         if (!\is_array($prefix)) {
             $this->route->addPrefix($prefix);
@@ -84,7 +84,7 @@ final public function prefix($prefix, bool $trailingSlashOnRoot = true)
      *
      * @return $this
      */
-    final public function namePrefix(string $namePrefix)
+    final public function namePrefix(string $namePrefix): self
     {
         $this->route->addNamePrefix($namePrefix);