The current check is too strict for newer makeinfo versions.
Existing version strings are:
makeinfo (GNU texinfo) 4.13
makeinfo (GNU texinfo) 5.2
texi2any (GNU texinfo) 5.9.93

Probably version 6 will come in the not too far future.
Reviewed-by: Timothy Gu <timothygu99@gmail.com>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>