Upgrade fastavro to 1.7.3

[BewareMyPower]

Fixes #67

This PR fixes the client cannot be installed with [avro]. Take Python 3.11 on Windows as example:

D:\> py -m pip install 'pulsar_client-3.2.0a1-cp311-cp311-win_amd64.whl[avro]'
Processing d:\pulsar_client-3.2.0a1-cp311-cp311-win_amd64.whl
Requirement already satisfied: certifi in c:\users\xuyunze\appdata\local\programs\python\python311\lib\site-packages (from pulsar-client==3.2.0a1) (2022.12.7)
Collecting fastavro==1.7.3
  Using cached fastavro-1.7.3-cp311-cp311-win_amd64.whl (406 kB)
pulsar-client is already installed with the same version as the provided wheel. Use --force-reinstall to force an installation of the wheel.
Installing collected packages: fastavro
Successfully installed fastavro-1.7.3

[notice] A new release of pip is available: 23.0.1 -> 23.1
[notice] To update, run: python.exe -m pip install --upgrade pip

TODO: fix the client cannot be installed with [all].

[merlimat]

Could we just remove the version here and let pip resolve the latest?

[tisonkun]

Fixed version or at least a ^x.y.z manner can prevent unintentional version bump?

[BewareMyPower]

If we let pip resolve the latest, maybe the support for some older Python versions might be dropped unexpectedly.

I think we should add extra workflows to verify the compatibility for the lowest version and highest version that we supported.