minor: Update README/CONTRIBUTING for EOL notice
minor: Update README/CONTRIBUTING for EOL notice

dagolden/mongo-perl-driver,dagolden/mongo-perl-driver,xdg/mongo-perl-driver,dagolden/mongo-perl-driver,xdg/mongo-perl-driver,dagolden/mongo-perl-driver,mongodb/mongo-perl-driver,mongodb/mongo-perl-driver,mongodb/mongo-perl-driver,xdg/mongo-perl-driver