Bump django-attachments from 1.4.1 to 1.5

Bumps [django-attachments](https://github.com/bartTC/django-attachments) from 1.4.1 to 1.5.
- [Release notes](https://github.com/bartTC/django-attachments/releases)
- [Changelog](https://github.com/bartTC/django-attachments/blob/master/CHANGELOG.rst)
- [Commits](bartTC/django-attachments@v1.4.1...v1.5)

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

requirements/base.txt

@@ -2,7 +2,7 @@
 
 bleach==3.1.0
 Django==2.2.8
-django-attachments==1.4.1
+django-attachments==1.5
 django-contrib-comments==1.9.2
 django-modern-rpc==0.12.0
 django-simple-history==2.8.0