Suppression handle unicode files

[mshafer-NI]

Found that Unicode symbols in code files broke acknowledge code

[mshafer-NI]

High level of change:

• bump pyproject.toml [too.poetry.dev-dependencies] pytest-snapshot from 0.4.2 to 0.6.3 or greater (utf-8 default was added in 0.5, and 0.6 added binary support, but had a bug fixed in 0.6.1, so requiring those fixed versions at minimum, but not pinning due to semantic versioning considering a 0.x bump to be a major bump)
• Add test case with ” (U+201D) - this was failing case that prompted investigation
• default acknowledge_existing_errors to use UTF-8 for reads and writes