Bump django from 2.2.4 to 2.2.6 in /requirements

Bumps [django](https://github.com/django/django) from 2.2.4 to 2.2.6.
- [Release notes](https://github.com/django/django/releases)
- [Commits](https://github.com/django/django/compare/2.2.4...2.2.6)

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

requirements/common.txt

@@ -39,9 +39,9 @@ Brotli==1.0.7 \
     --hash=sha256:113f51658e6fe548dce4b3749f6ef6c24de4184ba9c10a909cbee4261c2a5da0 \
     --hash=sha256:0538dc1744fd17c314d2adc409ea7d1b779783b89fd95bcfb0c2acc93a6ea5a7
 
-Django==2.2.4 \
-    --hash=sha256:9a2f98211ab474c710fcdad29c82f30fc14ce9917c7a70c3682162a624de4035 \
-    --hash=sha256:16a5d54411599780ac9dfe3b9b38f90f785c51259a584e0b24b6f14a7f69aae8
+Django==2.2.6 \
+    --hash=sha256:4025317ca01f75fc79250ff7262a06d8ba97cd4f82e93394b2a0a6a4a925caeb \
+    --hash=sha256:a8ca1033acac9f33995eb2209a6bf18a4681c3e5269a878e9a7e0b7384ed1ca3
 
 celery==4.3.0 --hash=sha256:528e56767ae7e43a16cfef24ee1062491f5754368d38fcfffa861cdb9ef219be --hash=sha256:4c4532aa683f170f40bd76f928b70bc06ff171a959e06e71bf35f2f9d6031ef9