Move U+03CF to GF Greek Expert

The Greek Capital Kai Symbol U+03CF `Ϗ` is not a character _for everyday Modern Greek_, as its position in GF Greek Core implies.
See: https://github.com/adobe-type-tools/adobe-greek-charsets/issues/1

The issue identifies U+03CF (Ϗ) and the GF Greek Core and GF Greek Expert glyphsets, but no file or test is named. Locate the definitions for those two glyphsets, confirm the character is currently in Core, and move it to Expert. Done means the character is no longer in Core and is present in Expert.

Written by the indexing model from the issue text.