Fix elicitation enum schema multiselect example

Author: pbezglasny

docs/specification/draft/client/elicitation.mdx

@@ -321,7 +321,7 @@ The schema is restricted to these primitive types:
      "minItems": 1,
      "maxItems": 2,
      "items": {
-       "oneOf": [
+       "anyOf": [
          { "const": "#FF0000", "title": "Red" },
          { "const": "#00FF00", "title": "Green" },
          { "const": "#0000FF", "title": "Blue" }