Update sbt-header to 5.11.0

[mzuehlke]

closes: #833

[rossabaker]

This is going to need to be a major version bump of this plugin, I think.

[armanbilge]

Indeed. Should bump the base version appropriately in this PR. Any compelling reasons to make this update?

[mzuehlke]

Correct
I will update the PR to update the base version

[rossabaker]

This update will be necessary for eventual SBT 2 support, I think? I don't think it's urgent in the short term, but needed in the long term.

I'm also contemplating an improvement to sbt-header's SPDX handling. That would be a subsequent release.

[mzuehlke]

As @rossabaker sad, we will need a newer version latest when we want to support sbt 2.
In the meantime it depends if we want to always include updates to all used sbt plugins.
Which would lead to more often base version bumps. Or do this very selectively.