Log Message:
shells/nushell: update to 0.39.0

Today, we're releasing 0.39 of Nu. This release is a bugfix release of 0.38.

What's New:
-History file is now removed when the history is cleared (fdncred)
-HTML selector has a regression fixed (lucassmmg)
-Unused dependencies were removed (lucassmmg)
-Updated clippy warnings were fixed (jt)

Engine-q progress
You'll notice that this release is pretty light, only a set of fixes on 0.38.
his is because our energy is now largely focused on engine-q.
We're excited to get this in front of you.

Just to tease a little of what will be possible, this week we added support for
processing streams in parallel in engine-q using a new par-each command.
We'll talk more about this as it develops.