RT-92547 remove sub pototypes

~/GitHub/Module-Install$ grep -r -P '\Asub\s+[\w|:]+\s+\(' .
./lib/Module/Install.pm:sub _version ($) {
./lib/Module/Install.pm:sub _cmp ($$) {
./lib/Module/Install.pm:sub _CLASS ($) {
./t/03_autoinstall.t:sub ExtUtils::MakeMaker::prompt ($;$) { return 'n' }