runtime: convert *_utf-8.vim files to actual UTF-8 encoding

runtime: convert *_utf-8.vim files to actual UTF-8 encoding

Several runtime files with "_utf-8" in their filename are actually encoded
in latin1 or cp1255, not UTF-8. This causes errors when tools attempt to
read these files as UTF-8.

Files converted:
- esperanto_utf-8.vim: latin1 -> UTF-8, updated scriptencoding directive
- greek_utf-8.vim: latin1 -> UTF-8
- hebrewp_utf-8.vim: cp1255 (Windows Hebrew) -> UTF-8
- menu_ca.utf-8.vim: latin1 -> UTF-8
- menu_ca_es.utf-8.vim: latin1 -> UTF-8
- menu_pt_pt.utf-8.vim: latin1 -> UTF-8

The actual functionality remains unchanged - only the encoding was modified.

closes: #16390

Signed-off-by: ThanhNguyxn <thanhnguyentuan2007@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>