Add typing_extensions requirement (#14244)

Add typing_extensions requirement.

Author: areusch

python/gen_requirements.py

@@ -72,6 +72,7 @@
                 "scipy",
                 "synr",
                 "tornado",
+                "typing_extensions",
             ],
         ),
     ),
@@ -277,6 +278,7 @@
     ("torch", None),
     ("torchvision", None),
     ("tornado", None),
+    ("typing_extensions", None),
     ("xgboost", ">=1.1.0,<1.6.0"),  # From PR #4953 & Issue #12009
 ]