Fix path of `file_get_contents`

Try to fix #28370  and #27441 

Avoid pre-pends the `$path` to the user's own storage.

lib/private/legacy/OC_Image.php

@@ -641,7 +641,7 @@ class OC_Image implements \OCP\IImage {
 			default:
 
 				// this is mostly file created from encrypted file
-				$this->resource = imagecreatefromstring(\OC\Files\Filesystem::file_get_contents(\OC\Files\Filesystem::getLocalPath($imagePath)));
+				$this->resource = imagecreatefromstring(file_get_contents(\OC\Files\Filesystem::getLocalPath($imagePath)));
 				$iType = IMAGETYPE_PNG;
 				$this->logger->debug('OC_Image->loadFromFile, Default', ['app' => 'core']);
 				break;