pytest-capturelog no longer exists

diff --git a/requirements-testing.txt b/requirements-testing.txt
index 1894122..c47d7b1 100644
--- a/requirements-testing.txt
+++ b/requirements-testing.txt
@@ -2,4 +2,3 @@ pytest
 pytest-cov
 coverage
 coveralls
-pytest-capturelog

When installing unit test dependencies from `requirements-testing.txt`, an error occurs:

```

 % virtualenv venv2

created virtual environment CPython3.6.9.final.0-64 in 3587ms

<…>

 % . venv2/bin/activate

 % pip3 install -e .

<…>

Successfully installed pexpect-4.8.0 ptyprocess-0.7.0

 % pip3 install -r requirements-testing.txt

<…>

ERROR: Could not find a version that satisfies the requirement pytest-capturelog (from versions: none)

ERROR: No matching distribution found for pytest-capturelog

 % py.test

zsh: command not found: py.test

```



It appears that the plugin `pytest-capturelog` no longer exists (https://pypi.org/project/pytest-capturelog/ returns 404 Not Found); its functionality has been merged into the pytest core since ~3.3 (see [deprecated.py](https://github.com/pytest-dev/pytest/blob/main/src/_pytest/deprecated.py#L17-L23)) and it should no longer be required.

[
  {
    "category": "misspecification",
    "rule": "signature.unresolvable_declared_requirement",
    "source": "failure_signature",
    "excerpt": "ERROR: Could not find a version that satisfies the requirement pytest-capturelog (from versions: none)"
  },
  {
    "category": "underspecification",
    "rule": "signature.missing_system_requirement",
    "source": "failure_signature",
    "excerpt": "ERROR: Could not find a version that satisfies the requirement pytest-capturelog (from versions: none)"
  }
]