chore(deps): update dependency pyflakes to v2.5.0

Author: renovate[bot]

requirements.txt

@@ -16,7 +16,7 @@ pickleshare==0.7.5
 prompt-toolkit==1.0.18
 ptyprocess==0.7.0
 pycodestyle==2.4.0
-pyflakes==2.0.0
+pyflakes==2.5.0
 Pygments==2.2.0
 simplegeneric==0.8.1
 six==1.17.0