(BUGFIX) Remove Oracle/Scientific Linux 6 from matrix_from_metadata_v2

Author: david22swan

exe/matrix_from_metadata_v2

@@ -49,10 +49,8 @@ DOCKER_PLATFORMS = {
   'Debian-10' => 'litmusimage/debian:10',
   'Debian-11' => 'litmusimage/debian:11',
   'Debian-12' => 'litmusimage/debian:12',
-  'OracleLinux-6' => 'litmusimage/oraclelinux:6',
   'OracleLinux-7' => 'litmusimage/oraclelinux:7',
   'OracleLinux-8' => 'litmusimage/oraclelinux:8',
-  'Scientific-6' => 'litmusimage/scientificlinux:6',
   'Scientific-7' => 'litmusimage/scientificlinux:7',
   'Ubuntu-18.04' => 'litmusimage/ubuntu:18.04',
   'Ubuntu-20.04' => 'litmusimage/ubuntu:20.04',