lib: Fix symbol versioning inheritance

I messed this up; the last release should inherit from the previous
release (N-1) and not the previous to that (N-2).

I think (hope) this isn't an ABI break...

Just noticed this when I was going to add a new symbol.

src/libostree/libostree-released.sym

@@ -681,7 +681,7 @@ LIBOSTREE_2022.4 {
 global:
   ostree_fs_get_all_xattrs;
   ostree_fs_get_all_xattrs_at;
-} LIBOSTREE_2021.5;
+} LIBOSTREE_2022.2;
 
 /* NOTE: Only add more content here in release commits!  See the
  * comments at the top of this file.