Clearer YAML style for flake8 extra plugin list

Author: EliahKagan

Diff for: .pre-commit-config.yaml

@@ -4,11 +4,9 @@ repos:
     hooks:
       - id: flake8
         additional_dependencies:
-          [
-            flake8-bugbear==23.9.16,
-            flake8-comprehensions==3.14.0,
-            flake8-typing-imports==1.14.0,
-          ]
+          - flake8-bugbear==23.9.16
+          - flake8-comprehensions==3.14.0
+          - flake8-typing-imports==1.14.0
         exclude: ^doc|^git/ext/
 
   - repo: https://github.com/pre-commit/pre-commit-hooks