Add extra help line for delete command

[sixfourtwelve]

Overview

Provides one extra help info for the delete command

Before:

.> help delete

  delete
  `delete foo` removes the term or type name `foo` from the namespace.

After:

.> help delete

  delete
  `delete foo` removes the term or type name `foo` from the namespace.
  `delete foo bar` removes the term or type name `foo` and `bar` from the namespace

Implementation notes

How does it accomplish it, in broad strokes? i.e. How does it change the Haskell codebase?

Test coverage

Manual testing

[sixfourtwelve]

Fixes #4194

[ceedubs]

Thank you! 🎉