PyG 2.5.1: Bugfixes

PyG 2.5.1 includes a variety of bugfixes.

Bug Fixes

• Ignore self.propagate appearances in comments when parsing MessagePassing implementation (#9044)
• Fixed OSError on read-only file systems within MessagePassing (#9032)
• Made MessagePassing interface thread-safe (#9001)
• Fixed metaclass conflict in Dataset (#8999)
• Fixed import errors on MessagePassing modules with nested inheritance (#8973)
• Fix OSError when downloading datasets with simplecache (#8932)

Full Changelog: 2.5.0...2.5.1