Bump tox from 3.24.2 to 3.24.3 (#131)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements_dev.txt

@@ -2,7 +2,7 @@
 bump2version==1.0.1
 wheel==0.37.0
 flake8==3.9.2
-tox==3.24.2
+tox==3.24.3
 coverage==5.5 # pyup: ignore
 twine==3.4.2
 mkdocs==1.2.2