Correct pyup ignore marker for pycodestyle

Since the breaking version is actually 2.4.0, not v3.

requirements/dev.txt

@@ -89,7 +89,7 @@ mccabe==0.6.1 \
     --hash=sha256:dd8d182285a0fe56bace7f45b5e7d1a6ebcbf524e8f3bd87eb0f125271b8831f
 pycodestyle==2.3.1 \
     --hash=sha256:6c4245ade1edfad79c3446fadfc96b0de2759662dc29d07d80a6f27ad1ca6ba9 \
-    --hash=sha256:682256a5b318149ca0d2a9185d365d8864a768a28db66a84a2ea946bcc426766  # pyup: <3 # Blocked on new release of flake8
+    --hash=sha256:682256a5b318149ca0d2a9185d365d8864a768a28db66a84a2ea946bcc426766  # pyup: <2.4.0 # Blocked on new release of flake8
 pyflakes==1.6.0 \
     --hash=sha256:08bd6a50edf8cffa9fa09a463063c425ecaaf10d1eb0335a7e8b1401aef89e6f \
     --hash=sha256:8d616a382f243dbf19b54743f280b80198be0bca3a5396f1d2e1fca6223e8805  # pyup: <2 # Blocked on new release of flake8