IMPALA-11398: Update flake8 in Gerrit review (part 2)

Updates the flake8 version used in critique-gerrit-review.py to 3.9.2 so
it recognizes the indent-size property.

Change-Id: Iae62749117ce1bf3d895b4ee4d024ffa8126ce04
Reviewed-on: http://gerrit.cloudera.org:8080/18685
Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>

Author: MikaelSmith

bin/jenkins/critique-gerrit-review.py

@@ -47,7 +47,7 @@
 import sys
 import virtualenv
 
-FLAKE8_VERSION = "3.5.0"
+FLAKE8_VERSION = "3.9.2"
 FLAKE8_DIFF_VERSION = "0.2.2"
 
 VENV_PATH = "gerrit_critic_venv"