Enable --strict-bytes checks in mypy (#3189)

Strict-bytes checks will be enabled by default in mypy 2.0, so this
commit will help prevent violations from being introduced into the
codebase.

pyproject.toml

@@ -78,6 +78,7 @@ disallow_untyped_decorators = true
 disallow_untyped_defs = true
 extra_checks = true
 strict = false
+strict_bytes = true
 strict_equality = true
 warn_redundant_casts = true
 warn_return_any = true