build: Explicitly add types-requests to development requirements.

djangorestframework-stubs==3.16.8 dropped types-requests as a
transitive dependency. Since edx-platform uses the requests library
directly, we need to pin types-requests explicitly so that mypy can
type-check our code correctly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: feanil

requirements/edx/development.in

@@ -21,5 +21,6 @@ django-stubs[compatible-mypy]           # Typing stubs for Django, so it works w
 djangorestframework-stubs               # Typing stubs for DRF
 mypy                                    # static type checking
 pywatchman                              # More efficient checking for runserver reload trigger events
+types-requests                          # Typing stubs for requests
 vulture                                 # Detects possible dead/unused code, used in scripts/find-dead-code.sh
 watchdog                                # Used by `npm run watch` to auto-recompile when assets are changed