Update the PyCQA/flake8 pre-commit hook

The previous version incorrectly triggers on some Python strings
containing colons so we need the updated hook here; otherwise, we get
errors that look like:
src/report/generate_https_scan_report.py:772:38: E231 missing whitespace after ':'
src/report/graphs.py:186:39: E231 missing whitespace after ':'
src/report/graphs.py:186:40: E231 missing whitespace after ','
src/report/graphs.py:586:77: E231 missing whitespace after ':'
src/report/graphs.py:589:47: E231 missing whitespace after ':'
src/report/graphs.py:640:74: E231 missing whitespace after ':'
src/report/graphs.py:641:66: E231 missing whitespace after ':'

.pre-commit-config.yaml

@@ -121,7 +121,7 @@ repos:
     hooks:
       - id: black
   - repo: https://github.com/PyCQA/flake8
-    rev: 6.0.0
+    rev: 6.1.0
     hooks:
       - id: flake8
         additional_dependencies: