Bump pysolr from 3.8.1 to 3.9.0

Bumps [pysolr](https://github.com/django-haystack/pysolr) from 3.8.1 to 3.9.0.
- [Release notes](https://github.com/django-haystack/pysolr/releases)
- [Changelog](https://github.com/django-haystack/pysolr/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/django-haystack/pysolr/compare/v3.8.1...v3.9.0)

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

requirements.txt

@@ -11,7 +11,7 @@ Pillow==7.2.0
 Whoosh==2.7.4
 django-environ==0.4.5
 django-redis==4.12.1
-pysolr==3.8.1
+pysolr==3.9.0
 redis==3.5.3
 requests==2.24.0
 uWSGI==2.0.19.1