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_lp 0.0.2.

Signed-off-by: Tim 'mithro' Ansell <me@mith.ro>
tree: f7f976f8d3ccc89bb8658ff22c1b352224551e6f
  1. cells/
  2. models/
  3. tech/
  4. timing/
  5. .gitignore
  6. LICENSE
  7. README.rst