Revert "Use APCu caching of composer"

This reverts commit 948ab8a4d0.

For details why see https://github.com/nextcloud/server/issues/11290

lib/base.php

@@ -895,8 +895,6 @@ class OC {
 				self::$loader->setMemoryCache($memcacheFactory->createLocal('Autoloader'));
 			} catch (\Exception $ex) {
 			}
-
-			self::$composerAutoloader->setApcuPrefix($instanceId . '-mainComposer');
 		}
 	}