Unskip test

Closes #3519381

core/tests/Drupal/Tests/Composer/Plugin/Scaffold/Functional/ScaffoldUpgradeTest.php

@@ -54,10 +54,6 @@ protected function setUp(): void {
    * Tests upgrading the Composer Scaffold plugin.
    */
   public function testScaffoldUpgrade(): void {
-    $composerVersionLine = exec('composer --version');
-    if (str_contains($composerVersionLine, 'Composer version 2')) {
-      $this->markTestSkipped('We cannot run the scaffold upgrade test with Composer 2 until we have a stable version of drupal/core-composer-scaffold to start from that we can install with Composer 2.x.');
-    }
     $this->fixturesDir = $this->fixtures->tmpDir($this->name());
     $replacements = ['SYMLINK' => 'false', 'PROJECT_ROOT' => $this->fixtures->projectRoot()];
     $this->fixtures->cloneFixtureProjects($this->fixturesDir, $replacements);
@@ -73,8 +69,9 @@ public function testScaffoldUpgrade(): void {
     // Packagist is disabled in the fixture; we bring it back by removing the
     // line that disables it.
     $this->mustExec("composer config --unset repositories.packagist.org", $sut);
-    $stdout = $this->mustExec("composer require --no-ansi drupal/core-composer-scaffold:8.8.0 --no-plugins 2>&1", $sut);
-    $this->assertStringContainsString("  - Installing drupal/core-composer-scaffold (8.8.0):", $stdout);
+    $this->mustExec("composer config --unset repositories.composer-scaffold", $sut);
+    $stdout = $this->mustExec("composer require --no-ansi drupal/core-composer-scaffold:9.5.0 --no-plugins 2>&1", $sut);
+    $this->assertStringContainsString("  - Installing drupal/core-composer-scaffold (9.5.0):", $stdout);
 
     // We can't force the path repo to re-install over the stable version
     // without removing it, and removing it masks the bugs we are testing for.