Bump widgetsnbextension in /etc/requirements_dependabot

Bumps [widgetsnbextension](http://jupyter.org) from 4.0.8 to 4.0.9.

---
updated-dependencies:
- dependency-name: widgetsnbextension
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

etc/requirements_dependabot/requirements_tests.txt

@@ -200,7 +200,7 @@ valimp==0.1
     # via market-prices
 wcwidth==0.2.6
     # via prompt-toolkit
-widgetsnbextension==4.0.8
+widgetsnbextension==4.0.9
     # via ipywidgets
 yahooquery==2.3.2
     # via market-prices