chore(app): Do not clear unused cache key

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

lib/private/App/AppManager.php

 	 * Clear the cached list of apps when enabling/disabling an app
 	 */
 	public function clearAppsCache() {
-		$settingsMemCache = $this->memCacheFactory->createDistributed('settings');
-		$settingsMemCache->clear('listApps');
 		$this->appInfos = [];
 	}
 

tests/lib/App/AppManagerTest.php

 		);
 	}
 
-	protected function expectClearCache() {
-		$this->cache->expects($this->once())
-			->method('clear')
-			->with('listApps');
-	}
-
 	public function testEnableApp() {
-		$this->expectClearCache();
 		// making sure "files_trashbin" is disabled
 		if ($this->manager->isEnabledForUser('files_trashbin')) {
 			$this->manager->disableApp('files_trashbin');
 	}
 
 	public function testDisableApp() {
-		$this->expectClearCache();
 		$this->eventDispatcher->expects($this->once())->method('dispatchTyped')->with(new AppDisableEvent('files_trashbin'));
 		$this->manager->disableApp('files_trashbin');
 		$this->assertEquals('no', $this->appConfig->getValue('files_trashbin', 'enabled', 'no'));
 			->willReturn('group2');
 
 		$groups = [$group1, $group2];
-		$this->expectClearCache();
 
 		/** @var AppManager|MockObject $manager */
 		$manager = $this->getMockBuilder(AppManager::class)
 			->willReturn('group2');
 
 		$groups = [$group1, $group2];
-		$this->expectClearCache();
 
 		/** @var AppManager|MockObject $manager */
 		$manager = $this->getMockBuilder(AppManager::class)