oci/tar: remove a pointless assert

This is a very old assert added during development and probably never
intended to remain.  Sometimes containers will be in non-ustar tar files
and that's OK.  In fact, the Fedora bootc image is one such example.

Signed-off-by: Allison Karlitskaya <[email protected]>

Author: allisonkarlitskaya

src/oci/tar.rs

@@ -176,7 +176,6 @@ pub fn get_entry<R: Read, ObjectID: FsVerityHashValue>(
         }
 
         let header = tar::Header::from_byte_slice(&buf);
-        assert!(header.as_ustar().is_some());
 
         let size = header.entry_size()?;