Swap out appdirs for platformdirs

* platformdirs is a more actively maintained fork of appdirs.
* Also relax requirements a bit for attrs and urllib (minimum instead of caret constraint)

Dependabot update:
Bump responses from 0.16.0 to 0.19.0

Bumps [responses](https://github.com/getsentry/responses) from 0.16.0 to 0.19.0.
- [Release notes](https://github.com/getsentry/responses/releases)
- [Changelog](https://github.com/getsentry/responses/blob/master/CHANGES)
- [Commits](https://github.com/getsentry/responses/compare/0.16.0...0.19.0)

---
updated-dependencies:
- dependency-name: responses
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

2 files changed, 2 insertions, 2 deletions

diff --git a/tests/integration/test_filesystem.py b/tests/integration/test_filesystem.py
index b651186..1b81dff 100644
--- a/tests/integration/test_filesystem.py
+++ b/tests/integration/test_filesystem.py
@@ -2,7 +2,7 @@ from shutil import rmtree
 from tempfile import gettempdir
 
 import pytest
-from appdirs import user_cache_dir
+from platformdirs import user_cache_dir
 
 from requests_cache.backends import FileCache, FileDict
 from requests_cache.serializers import SERIALIZERS, SerializerPipeline
diff --git a/tests/integration/test_sqlite.py b/tests/integration/test_sqlite.py
index 1840a78..391d46b 100644
--- a/tests/integration/test_sqlite.py
+++ b/tests/integration/test_sqlite.py
@@ -5,7 +5,7 @@ from threading import Thread
 from unittest.mock import patch
 
 import pytest
-from appdirs import user_cache_dir
+from platformdirs import user_cache_dir
 
 from requests_cache.backends.base import BaseCache
 from requests_cache.backends.sqlite import MEMORY_URI, SQLiteCache, SQLiteDict, SQLitePickleDict