Add proto-plus as a direct dependency #523
Description
proto-plus should be added as a direct dependency as it's used in this repository
https://github.com/search?q=repo%3Agoogleapis%2Fpython-pubsublite+%22import+proto%22&type=code
Update dependencies in setup.py to include the following lines
"proto-plus >= 1.22.3, < 2.0.0dev",
"proto-plus >= 1.25.0, < 2.0.0dev; python_version >= '3.13'",
Lines 38 to 45 in b868888