Install univers from pypi

Signed-off-by: Shivam Sandbhor <shivam.sandbhor@gmail.com>

Author: sbs2001

requirements.txt

@@ -7,7 +7,7 @@ cached-property==1.5.1
 cffi==1.14.0
 contextlib2==0.5.5
 decorator==4.4.2
-univers @ git+https://github.com/sbs2001/univers.git
+univers==21.4.8
 dj-database-url==0.4.2
 Django==3.0.13
 django-filter==2.2.0