Fixes Psalm's "InvalidArgument" error.

I just removed the return type from the "exceptionErrorHandler". There is in fact a hacky solution, that I didn't like:
vimeo/psalm#3571

Signed-off-by: Faraz Samapoor <fsa@adlas.at>

apps/files/lib/Command/ScanAppData.php

@@ -182,7 +182,7 @@ protected function initTools(): void {
 	 *
 	 * @throws \ErrorException
 	 */
-	public function exceptionErrorHandler($severity, $message, $file, $line): void {
+	public function exceptionErrorHandler($severity, $message, $file, $line) {
 		if (!(error_reporting() & $severity)) {
 			// This error code is not included in error_reporting
 			return;