sshkey provider broken with Puppet 6

[raphink]

puppetlabs/puppetlabs-sshkeys_core#27 breaks compatibility by making type a parameter.

[raphink]

The easiest option will be to stop managing type as a property, though this will remove that feature in Puppet 5, which cannot manage it as a param.

[yakatz]

Puppet 5 and 6 are no longer supported. Is this still relevant?

[ekohl]

Looks like this is the cause for the failures seen in #97.

[yakatz]

Amazing that no one else has run into this in 4 years...

[alexjfisher]

Also... should this provider actually declare itself as the default provider? I'm using this module for one of the other types and have just discovered it has taken over managing sshkey resources. And it's much slower...

[alexjfisher]

I've opened #106