Speed up get_framework_suppliers endpoint
Speed up get_framework_suppliers endpoint

Admin app listing of suppliers on a framework has been intermittently timing out.

This patch will hopefully help by speeding up the API request.

Local testing looks promising... timing 5000 requests using the API client `find_framework_suppliers` method with various different params set (G7, G8, with and without agreement returned, with statuses set) results were as follows:
Unpatched (current master branch): 04:42.557284
Patched (this branch):  02:34.732294

i.e. almost halved the time taken for 5000 requests.

alphagov/digitalmarketplace-api,alphagov/digitalmarketplace-api,alphagov/digitalmarketplace-api