Merge bitcoin/bitcoin#28194: test: python E721 and flake8 updates

bee2d57a655645dbfaf0242e85c5af034023a2fb script: update flake8 to 6.1.0 (Jon Atack)
38c3fd846bff163eb7c50bd77efcdcf8fcbc7f43 test: python E721 updates (Jon Atack)

Pull request description:

  Update our functional tests per [E721](https://www.flake8rules.com/rules/E721.html) enforced by [flake8 6.1.0](https://flake8.pycqa.org/en/latest/release-notes/6.1.0.html), and update our CI lint task to use that release.  This makes the following linter output on current master with flake8 6.1.0 green.

  ```
  $ ./test/lint/lint-python.py ; ./test/lint/lint-spelling.py
  test/functional/p2p_invalid_locator.py:35:16: E721 do not compare types, for exact checks use `is` / `is not`, for instance checks use `isinstance()`
  test/functional/test_framework/siphash.py:34:12: E721 do not compare types, for exact checks use `is` / `is not`, for instance checks use `isinstance()`
  test/functional/test_framework/siphash.py:64:12: E721 do not compare types, for exact checks use `is` / `is not`, for instance checks use `isinstance()`
  src/test/fuzz/descriptor_parse.cpp:88: occurences ==> occurrences
  ^ Warning: codespell identified likely spelling errors. Any false positives? Add them to the list of ignored words in test/lint/spelling.ignore-words.txt
  ```

ACKs for top commit:
  MarcoFalke:
    lgtm ACK bee2d57a655645dbfaf0242e85c5af034023a2fb

Tree-SHA512: f3788a543ca98e44eeeba1d06c32f1b11eec95d4aef068aa1b6b5c401261adfa3fb6c6d6c769f3fe6839d78e74a310d5c926867e7c367d6513a53d580fd376f3

1 files changed, 1 insertions, 1 deletions

diff --git a/src/test/fuzz/descriptor_parse.cpp b/src/test/fuzz/descriptor_parse.cpp
index b879b0d141..8ed659323c 100644
--- a/src/test/fuzz/descriptor_parse.cpp
+++ b/src/test/fuzz/descriptor_parse.cpp
@@ -85,7 +85,7 @@ public:
         std::string desc;
         desc.reserve(mocked_desc.size());
 
-        // Replace all occurences of '%' followed by two hex characters with the corresponding key.
+        // Replace all occurrences of '%' followed by two hex characters with the corresponding key.
         for (size_t i = 0; i < mocked_desc.size();) {
             if (mocked_desc[i] == '%') {
                 if (i + 3 >= mocked_desc.size()) return {};