add jinja2 to fastapi test dependencies

Author: alexander-alderman-webb

scripts/populate_tox/config.py

@@ -123,6 +123,7 @@
                 "python-multipart",
                 "requests",
                 "anyio<4",
+                "jinja2",
             ],
             # There's an incompatibility between FastAPI's TestClient, which is
             # actually Starlette's TestClient, which is actually httpx's Client.