Dropped file_permissions_grub2_cfg remediation from rhel6

per ianko's comments @
https://github.com/OpenSCAP/scap-security-guide/pull/250
Moved file_permissions_grub2_cfg.sh from shared/ to rhel7 fixes

per https://github.com/OpenSCAP/scap-security-guide/pull/250
Merge pull request #257 from shawndwells/file_permissions_grub2_cfg

delinked grub2 remediation