Fix `CLASS` for fill_diode LEF files.

Replace `CLASS SPACER` with `CLASS CORE SPACER`.

Fixes https://github.com/google/skywater-pdk/issues/141.

Signed-off-by: Tim 'mithro' Ansell <tansell@google.com>

README.rst

diff --git a/README.rst b/README.rst
index 2c3b62b..541dc4c 100644
--- a/README.rst
+++ b/README.rst
@@ -1,5 +1,5 @@
 :lib:`sky130_fd_sc_hs` - SKY130 High Speed Digital Standard Cells (SkyWater Provided)
 =====================================================================================
 
-Initial release of version (0, 0, 0).
+Initial release of version (0, 0, 1).