Remove async functionality from ZI base class

[ysalatheZI]

Please use the following template for a pull request.

Fixes #issuenumber.

Changes proposed in this pull request:

• remove misleading and unused async functionality from the ZI base instrument class

@jul-sm

In order for the pull request to be merged, the following conditions must be met:

• test suite (Github actions) passes
• all reasonable issues raised by codacy must be resolved
• a positive review is required

Whenever possible the pull request should

• follow the PEP8 style guide
• have tests for the code
• be well documented and contain comments

Tests are not mandatory as this is generally hard to make for instruments that interact with hardware.