Update pyvisa to 1.11.3

[pyup-bot]

This PR updates pyvisa from 1.10.1 to 1.11.3.

Changelog

1.11.3

-------------------

1.11.2 was skipped due to an issue in the MANIFEST file.

- fix MANIFEST to exclude built docs
- fix minor typos in deprecation warning for GPIB resources
- generate some test files on the fly to avoid issue when building conda packages
- add official Python 3.9 support

1.11.1

-------------------

- deprecate methods that were mistakenly added to GPIB::INSTR resources PR 560
- fix the listing of available backends (Also not that we now return the backend
name as can be used to create a ResourceManger) PR 545
- allow a None value for the board value of a ResourceInfo PR 547
This allows for funky resource name such ASRL/dev/tty0::INSTR which are common
in pyvisa-py and avoid returning a completely generic resource in those cases.

Links

• PyPI: https://pypi.org/project/pyvisa
• Changelog: https://pyup.io/changelogs/pyvisa/
• Repo: https://github.com/pyvisa/pyvisa