python3Packages.aria2p: Change python3Packages.appdirs to python3Packages.platformdirs in dependencies

nixpkgs commit 5f91e2ea80 updated aria2p
from 0.12.0 to 0.12.1, breaking the build. The changelog for 0.12.1
(https://github.com/pawamoy/aria2p/blob/0.12.1/CHANGELOG.md) shows upstream
changed from the appdirs package to platformdirs, but this change
wasn't made in the above nixpkgs commit.

pkgs/development/python-modules/aria2p/default.nix

@@ -4,8 +4,8 @@
   fetchFromGitHub,
   pythonOlder,
   pdm-backend,
-  appdirs,
   loguru,
+  platformdirs,
   requests,
   setuptools,
   toml,
@@ -37,8 +37,8 @@ buildPythonPackage rec {
   build-system = [ pdm-backend ];
 
   dependencies = [
-    appdirs
     loguru
+    platformdirs
     requests
     setuptools # for pkg_resources
     toml