Remove jinja2 pin.

Author: rossbar

setup.py

@@ -43,7 +43,7 @@ def read(fname):
     author_email="[email protected]",
     url="https://numpydoc.readthedocs.io",
     license="BSD",
-    install_requires=["sphinx>=1.8", 'Jinja2>=2.10,<3.1'],
+    install_requires=["sphinx>=1.8", 'Jinja2>=2.10'],
     python_requires=">=3.7",
     extras_require={
         "testing": [