HOT-FIX: atualiza Weasyprint por conta de bug e requirements.txt

Atualiza Weasyprint por conta do bug
https://github.com/Kozea/WeasyPrint/issues/953

E também atualiza requirements porque rede senado não aceita protocolo
git.

requirements/requirements.txt

@@ -24,7 +24,7 @@ pytz==2019.3
 rtyaml==0.0.5
 python-magic==0.4.15
 unipath==1.1
-WeasyPrint==50
+WeasyPrint==51
 Pillow==6.2.0
 gunicorn==19.9.0
 kombu==4.2.0
@@ -44,6 +44,6 @@ daphne==2.2.5
 channels_redis==2.3.2
 channels==2.1.7
 
-git+git://github.com/interlegis/trml2pdf.git
+git+https://github.com/interlegis/trml2pdf
-git+git://github.com/interlegis/django-admin-bootstrapped
+git+https://github.com/interlegis/django-admin-bootstrapped
-cryptography==2.7
+cryptography==2.7