Bug 18120: Update field descriptions

Trying to clarify some of the descriptions.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

api/v1/swagger/definitions/vendor.json

@@ -106,7 +106,7 @@
         "boolean",
         "null"
       ],
-      "description": "Is the library taxed when buying to this vendor"
+      "description": "Is the library taxed when buying from this vendor"
     },
     "list_includes_gst": {
       "type": [
@@ -127,21 +127,21 @@
         "number",
         "null"
       ],
-      "description": "Tax rate"
+      "description": "Default tax rate for items ordered from this vendor"
     },
     "discount": {
       "type": [
         "number",
         "null"
       ],
-      "description": "Discount offered on all items ordered from this vendor"
+      "description": "Default discount rate for items ordered from this vendor"
     },
     "deliverytime": {
       "type": [
         "integer",
         "null"
       ],
-      "description": "Vendor expected delivery time (in days)"
+      "description": "Expected delivery time (in days)"
     }
   },
   "additionalProperties": false,