Update dependency django-phonenumber-field to v4

This MR contains the following updates:

Package	Type	Update	Change
django-phonenumber-field	dependencies	major	^3.0 -> ^4.0

---

Renovate configuration

Schedule: At any time (no schedule defined).

Automerge: Disabled by config. Please merge this manually once you are satisfied.

Rebasing: Whenever MR becomes conflicted.

Ignore: Close this MR and you won't be reminded about this update again.

---

• If you want to rebase/retry this MR, check this box

---

This MR has been generated by Renovate Bot.

pyproject.toml

@@ -30,7 +30,7 @@ django-middleware-global-request = "^0.1.2"
 django-menu-generator = "^1.0.4"
 django-tables2 = "^2.1"
 Pillow = "^6.1"
-django-phonenumber-field = {version = "^3.0", extras = ["phonenumbers"]}
+django-phonenumber-field = {version = "^4.0", extras = ["phonenumbers"]}
 django-sass-processor = "^0.7.3"
 libsass = "^0.19.2"
 colour = "^0.1.5"