Remove root-path from file provider

Tag no longer exists and might be the reason for crashes on some
devices in androidx.core.content.FileProvider.parsePathStrategy
(which is outside of AntennaPod).

app/src/main/res/xml/provider_paths.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <paths>
     <external-path name="external_storage" path="."/>
-    <root-path name="external_files" path="/storage/" />
+    <files-path name="name" path="." />
 </paths>