Bump webob from 1.4 to 1.8.8

Bumps [webob](https://github.com/Pylons/webob) from 1.4 to 1.8.8.
- [Changelog](https://github.com/Pylons/webob/blob/main/CHANGES.txt)
- [Commits](Pylons/webob@1.4...1.8.8)

---
updated-dependencies:
- dependency-name: webob
  dependency-type: direct:production
...

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

requirements.txt

@@ -118,7 +118,7 @@ pygeocoder==1.2.5
 # mysociety-Django-Select2==4.3.2.2
 -e git+https://github.com/mysociety/django-select2@28c9bf981017d83836390b264a0fa8dd246e6a07#egg=Django-Select2
 Shapely==1.5.0
-WebOb==1.4
+WebOb==1.8.8
 amqp==1.4.6
 anyjson==0.3.3
 audioread==1.0.3