iso-8859-6.7, iso_8859_6.7: Fix file misnaming: s/9959/8859/

Reported-by: Lefteris Dimitroulakis <edimitro@tee.gr>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man7/iso-9959-6.7 b/man7/iso-8859-6.7
similarity index 100%
rename from man7/iso-9959-6.7
rename to man7/iso-8859-6.7

diff --git a/man7/iso_9959_6.7 b/man7/iso_8859_6.7
similarity index 100%
rename from man7/iso_9959_6.7
rename to man7/iso_8859_6.7