TEST: Bump rtols to fix flaky tests

[derb12]

Description

Slightly bumps the relative tolerances for a few tests to address the flaky CI behavior seen in #51, #53, #58, and #59.

Locally, for new venvs with the same os, python, numpy, scipy, and openblas versions, I can consistently reproduce the test failures on one machine (AMD cpu) but not another (Intel cpu, not using mkl), so these flaky tests may just have a small architecture dependence? When the tests fail, both on the CI and locally, they always produce the same output, so it's not like the output is random. Not worth devoting more time to this since simply bumping the rtol by half a magnitude addresses all failures.

Type of Pull Request

• Bug Fix
• New Feature
• Miscellaneous Changes (refactor, code improvements, etc.)
• Documentation or Example Programs

Pull Request Checklist

• New code and/or documentation is valid for use with the BSD 3-clause license.
• [n/a] New code is fully documented with docstrings that follow Numpy style,
  if applicable.
• [n/a] New code follows PEP 8 standards as closely as possible, if applicable.
• Added/updated tests and ensured they pass locally, if applicable.
• [n/a] Verified that documentation builds locally, if applicable.