compat/winansi: drop pre-Vista workaround

compat/winansi: drop pre-Vista workaround

1edeb9a (Win32: warn if the console font doesn't support Unicode,
2014-06-10) introduced both code to detect the current console font on
Windows Vista and newer and a fallback for older systems to detect the
default console font and issue a warning if that font doesn't support
unicode.

Since we haven't supported any Windows older than Vista in almost a
decade, we don't need to keep the workaround.

Signed-off-by: Matthias Aßhauer <redacted>
Signed-off-by: Johannes Schindelin <redacted>
Signed-off-by: Junio C Hamano <redacted>