musikr: recursively clean files

Helps clean out any previous folders from the old revisioned covers
system.

musikr/src/main/java/org/oxycblt/musikr/covers/stored/CoverStorage.kt

@@ -136,7 +136,7 @@ private class FSCoverStorage(private val dir: File) : CoverStorage {
         }
 
     override suspend fun rm(name: String) {
-        withContext(Dispatchers.IO) { File(dir, name).delete() }
+        withContext(Dispatchers.IO) { File(dir, name).deleteRecursively() }
     }
 }