chore(test): correct #871 -> #932 issue references in merged ri-exchange Azure cred tests #26

Merged PR LeanerCloud/cloud-commitments-cli#934 fixes LeanerCloud/cloud-commitments-cli#932 (Azure RI-exchange per-subscription credential resolution) but its branch name (fix/871-azure-ri-credentials) and test comments in internal/api/handler_ri_exchange_test.go (~lines 811, 829) reference LeanerCloud/cloud-commitments-cli#871 - an unrelated, closed type/question design issue. Cosmetic traceability cleanup: update those comment references to LeanerCloud/cloud-commitments-cli#932. No behavior change. Found during adversarial verification of LeanerCloud/cloud-commitments-cli#934 (functionally VERIFIED-CORRECT).