clean up remaining deprecations

Author: xabbuh

Filesystem.php

@@ -600,10 +600,6 @@ public function mirror($originDir, $targetDir, \Traversable $iterator = null, $o
      */
     public function isAbsolutePath($file)
     {
-        if (null === $file) {
-            @trigger_error(sprintf('Calling "%s()" with a null in the $file argument is deprecated since Symfony 4.4.', __METHOD__), E_USER_DEPRECATED);
-        }
-
         return strspn($file, '/\\', 0, 1)
             || (\strlen($file) > 3 && ctype_alpha($file[0])
                 && ':' === $file[1]

Tests/FilesystemTest.php

@@ -1400,15 +1400,6 @@ public function providePathsForIsAbsolutePath()
         ];
     }
 
-    /**
-     * @group legacy
-     * @expectedDeprecation Calling "Symfony\Component\Filesystem\Filesystem::isAbsolutePath()" with a null in the $file argument is deprecated since Symfony 4.4.
-     */
-    public function testIsAbsolutePathWithNull()
-    {
-        $this->assertFalse($this->filesystem->isAbsolutePath(null));
-    }
-
     public function testTempnam()
     {
         $dirname = $this->workspace;