Downgrade pygments to v 2.4.2

Signed-off-by: Jono Yang <jyang@nexb.com>

Author: JonoYang

setup.cfg

@@ -33,7 +33,7 @@ install_requires =
 	commoncode
 	pdfminer.six
 	plugincode
-	pygments >= 2.7.1
+	pygments == 2.4.2
 	six
 setup_requires = setuptools_scm[toml] >= 4