Bump pip-tools from 5.5.0 to 6.0.0

Bumps [pip-tools](https://github.com/jazzband/pip-tools) from 5.5.0 to 6.0.0.
- [Release notes](https://github.com/jazzband/pip-tools/releases)
- [Changelog](https://github.com/jazzband/pip-tools/blob/master/CHANGELOG.md)
- [Commits](jazzband/pip-tools@5.5.0...6.0.0)

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

requirements/dev.txt

@@ -4,14 +4,10 @@
 #
 #    pip-compile --output-file=requirements/dev.txt requirements/dev.in
 #
-atomicwrites==1.4.0
-    # via pytest
 attrs==20.3.0
     # via pytest
 click==7.1.2
     # via pip-tools
-colorama==0.4.4
-    # via pytest
 coverage==5.4
     # via pytest-cov
 iniconfig==1.1.1
@@ -26,7 +22,7 @@ markupsafe==1.1.1
     #   mako
 packaging==20.9
     # via pytest
-pip-tools==5.5.0
+pip-tools==6.0.0
     # via -r requirements/dev.in
 pluggy==0.13.1
     # via pytest