Update flake8 requirement from ==4.* to ==5.* in /allure-robotframework

Updates the requirements on [flake8](https://github.com/pycqa/flake8) to permit the latest version.
- [Release notes](https://github.com/pycqa/flake8/releases)
- [Commits](PyCQA/flake8@4.0.0...5.0.4)

---
updated-dependencies:
- dependency-name: flake8
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

allure-robotframework/requirements.txt

@@ -5,5 +5,5 @@ pyhamcrest
 six
 poethepoet
 # linters
-flake8==4.*
+flake8==5.*
 flake8-builtins