fix: remove defunct payment gateway links from ERPNext Integrations workspace

- Remove GoCardless Settings link (DocType deleted in v15.0)
- Remove Mpesa Settings link (DocType deleted in v15.0)
- Update Payments card link_count from 3 to 1
- Only Plaid Settings remains in Payments section

Fixes broken links that resulted in errors when clicked.
Closes #49352

erpnext/erpnext_integrations/workspace/erpnext_integrations/erpnext_integrations.json

@@ -188,30 +188,10 @@
    "hidden": 0,
    "is_query_report": 0,
    "label": "Payments",
-   "link_count": 3,
+   "link_count": 1,
    "onboard": 0,
    "type": "Card Break"
   },
-  {
-   "hidden": 0,
-   "is_query_report": 0,
-   "label": "GoCardless Settings",
-   "link_count": 0,
-   "link_to": "GoCardless Settings",
-   "link_type": "DocType",
-   "onboard": 0,
-   "type": "Link"
-  },
-  {
-   "hidden": 0,
-   "is_query_report": 0,
-   "label": "Mpesa Settings",
-   "link_count": 0,
-   "link_to": "Mpesa Settings",
-   "link_type": "DocType",
-   "onboard": 0,
-   "type": "Link"
-  },
   {
    "hidden": 0,
    "is_query_report": 0,