Fixing LEF 'CLASS' on fill cells.

The fill cells should have 'CLASS' of 'CORE SPACER' in the LEF.

All fill cells should now have;
```lef
  CLASS CORE SPACER ;
```

Updating sky130_fd_sc_hs 0.0.1.

Signed-off-by: Tim 'mithro' Ansell <me@mith.ro>