fix: remove the single use of a union type in the api

[eseidel]

Union types are easy in typescript, but harder in languages
like rust, c++, dart, etc. The Dart openapi generator doesn't
currently support oneOf (that could be fixed), and since this is
the only place it's used it seems like a low cost to remove it.

The cost is mild ergnomics for easier generation by language that
lack union types (at least with generators that generate a type
for every argument declaration).

[eseidel]

This was removed for a while, but just added back again. 😦

@@ -3355,10 +3396,17 @@
                     },
                     {
                         "schema": {
-                            "type": "array",
-                            "items": {
-                                "$ref": "#/components/schemas/WaypointTraitSymbol"
-                            }
+                            "anyOf": [
+                                {
+                                    "type": "array",
+                                    "items": {
+                                        "$ref": "#/components/schemas/WaypointTraitSymbol"
+                                    }
+                                },
+                                {
+                                    "$ref": "#/components/schemas/WaypointTraitSymbol"
+                                }
+                            ]
                         },
                         "in": "query",
                         "name": "traits",

Would love to see it removed again (just go back to accepting the array) so I don't have to teach my generator about anyOf for this one case. 🙃