build: disable ALLOW_UNICODE option flag for doctest

This change removes the `ALLOW_UNICODE` option flag for doctests as this
accommodated the use of Unicode literals in docstrings, which has since all
been eliminated.

Docstrings should not use Unicode literals (i.e. `u'Litéral'`) as they are redundant
in Python 3 given all strings are Unicode strings.

Related issues:
- Closes <#2378>

Signed-off-by: Alex Nelson <alexander.nelson@nist.gov>

pyproject.toml

@@ -198,7 +198,6 @@ addopts = [
    "--doctest-glob=docs/*.rst",
    "--strict-markers",
 ]
-doctest_optionflags = "ALLOW_UNICODE"
 filterwarnings = [
     # The below warning is a consequence of how pytest doctest detects mocks and how DefinedNamespace behaves when an undefined attribute is being accessed.
     "ignore:Code. pytest_mock_example_attribute_that_shouldnt_exist is not defined in namespace .*:UserWarning",