Replace deprecated switches

Warning: -convert-to is deprecated.  Use --convert-to instead.
Warning: -outdir is deprecated.  Use --outdir instead.

lib/private/preview/office-cl.php

@@ -29,7 +29,7 @@ if (!\OC_Util::runningOnWindows()) {
 
 			$tmpDir = get_temp_dir();
 
-			$defaultParameters = ' -env:UserInstallation=file://' . escapeshellarg($tmpDir . '/owncloud-' . \OC_Util::getInstanceId().'/') . ' --headless --nologo --nofirststartwizard --invisible --norestore -convert-to pdf -outdir ';
+			$defaultParameters = ' -env:UserInstallation=file://' . escapeshellarg($tmpDir . '/owncloud-' . \OC_Util::getInstanceId().'/') . ' --headless --nologo --nofirststartwizard --invisible --norestore --convert-to pdf --outdir ';
 			$clParameters = \OCP\Config::getSystemValue('preview_office_cl_parameters', $defaultParameters);
 
 			$exec = $this->cmd . $clParameters . escapeshellarg($tmpDir) . ' ' . escapeshellarg($absPath);