Removed unused partner parameter from Swagger view for programs list endpoint

We haven't used this parameter for quite some time. It doesn't work, and should not be shown on the Swagger page.

course_discovery/apps/api/v1/views/programs.py

@@ -47,12 +47,6 @@ class ProgramViewSet(CacheResponseMixin, viewsets.ReadOnlyModelViewSet):
         """ List all programs.
         ---
         parameters:
-            - name: partner
-              description: Filter by partner
-              required: false
-              type: string
-              paramType: query
-              multiple: false
             - name: marketable
               description: Retrieve marketable programs. A program is considered marketable if it is active
                 and has a marketing slug.