Remove Mdm::CredFile

[#41837027]

Mdm::CredFile is only using Pro, so it is being removed from this
repository and moved to pro's repository (and renamed to just CredFile).
Merge branch 'master' into bug/cred-file-pro-only
Bump version

[#41837027]
Merge pull request #7 from rapid7/bug/cred-file-pro-only

Remove Mdm::CredFile