Remove netmhcii specs and deactivate corresponding tests

[christopher-mohr]

This removes the support for the tools netmhcII and netmhcIIpan since the versions that supported by FRED2 are not provided anymore by the developer of the netmhc tools. We will probably add more recent versions of these tools again later.

I kept the parameters for the tool executables and the test profiles, but we can discuss if it would be better to remove these as well for now.

PR checklist

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated
• If necessary, also make a PR on the nf-core/epitopeprediction branch on the nf-core/test-datasets repo

[ggabernet]

Looks good to me!