fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-DJANGO-1066259
- https://snyk.io/vuln/SNYK-PYTHON-DJANGO-1076802
- https://snyk.io/vuln/SNYK-PYTHON-JINJA2-1012994
- https://snyk.io/vuln/SNYK-PYTHON-PILLOW-1080635
- https://snyk.io/vuln/SNYK-PYTHON-PILLOW-1080654
- https://snyk.io/vuln/SNYK-PYTHON-PILLOW-1081494
- https://snyk.io/vuln/SNYK-PYTHON-PILLOW-1081501
- https://snyk.io/vuln/SNYK-PYTHON-PILLOW-1081502
- https://snyk.io/vuln/SNYK-PYTHON-PILLOW-1082329
- https://snyk.io/vuln/SNYK-PYTHON-PILLOW-1082750

requirements.txt

@@ -63,7 +63,7 @@ django-sass-processor==0.7
     # via -r requirements.in
 git+https://github.com/City-of-Helsinki/django-translation-checker.git@master
     # via -r requirements.in
-django==2.2.17
+django==2.2.18
     # via
     #   -r requirements.in
     #   django-allauth
@@ -95,7 +95,7 @@ isodate==0.6.0
     # via python3-saml
 itypes==1.1.0
     # via coreapi
-jinja2==2.10.1
+jinja2==2.11.3
     # via coreschema
 jwcrypto==0.6.0
     # via -r requirements.in
@@ -112,7 +112,7 @@ oauthlib==2.1.0
     #   django-oauth-toolkit
     #   requests-oauthlib
     #   social-auth-core
-pillow==8.1.0
+pillow==8.1.1
     # via -r requirements.in
 polib==1.1.0
     # via django-translation-checker