Update beautifulsoup4 requirement from ==4.8.* to ==4.9.* (#451)

Updates the requirements on [beautifulsoup4](http://www.crummy.com/software/BeautifulSoup/bs4/) to permit the latest version.

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

requirements/test.txt

@@ -7,5 +7,5 @@ isort==4.3.*
 flake8==3.7.*
 pep8==1.7.*
 # for checking html
-beautifulsoup4==4.8.*
+beautifulsoup4==4.9.*
 Pillow==7.1.*