Merge pull request #2795 from nextcloud/techdept/unused-imports

lib/AppInfo/BootstrapSingleton.php

lib/Command/DiagnoseAccount.php

lib/Contracts/IMailManager.php

lib/Db/Mailbox.php

lib/Db/MailboxMapper.php

lib/Http/Middleware/ProvisioningMiddleware.php

lib/Http/ProxyDownloadResponse.php

lib/IMAP/MessageMapper.php

lib/Mailbox.php

lib/Migration/Version0156Date20190828140357.php

lib/Migration/Version0161Date20190902114635.php

lib/Migration/Version0190Date20191118160843.php

lib/Migration/Version1030Date20200228105714.php

lib/Model/IMAPMessage.php

lib/Model/IMessage.php

lib/Model/Message.php

lib/Model/NewMessageData.php

lib/SMTP/SmtpClientFactory.php

lib/Service/Attachment/AttachmentService.php

lib/Service/HtmlPurify/TransformCSSBackground.php