remove again nonexistent from-* entries from vt INDEX.keymaps

A number of entries of the form "de.kbd.from-cp850" existed in vt's
INDEX.keymaps, added in r270114, but these files do not exist.

I removed them in r355585 but accidentally re-added them in r355592.
Remove them yet again.

PR: 235564, 235853
MFC after: 1 week