fix: made secondary_text response optional (googlemaps#446)

Author: nora-soderlund

specification/schemas/PlaceAutocompleteStructuredFormat.yml

@@ -17,7 +17,6 @@ title: PlaceAutocompleteStructuredFormat
 required:
   - main_text
   - main_text_matched_substrings
-  - secondary_text
 properties:
   main_text:
     description: Contains the main text of a prediction, usually the name of the place.
@@ -34,4 +33,4 @@ properties:
     description: Contains an array with `offset` value and `length`. These describe the location of the entered term in the prediction result text, so that the term can be highlighted if desired.
     type: array
     items:
-      $ref: "./PlaceAutocompleteMatchedSubstring.yml"
+      $ref: "./PlaceAutocompleteMatchedSubstring.yml"