Remove unnecessary iterator in Language.pipe

[adrianeboyd]

Description

Remove iterator over raw_texts with iterator.tee() in Language.pipe that is never consumed and consumes memory unnecessarily.

Addresses part of issue in #5083. I think the use of iterator.tee() may still be causing memory problems with multiprocessing, but this should be an improvement for .pipe(n_process=1).

Types of change

Checklist

• I have submitted the spaCy Contributor Agreement.
• I ran the tests, and all new and existing tests passed.
• My changes don't require a change to the documentation, or if they do, I've added all required information.