Fix conditional requirement on privacy and terms last_updated (#693)

gbfs.md

@@ -517,9 +517,9 @@ Field Name | REQUIRED | Type | Defines
 `brand_assets.brand_image_url_dark` <br/>*(added in v2.3)*  | OPTIONAL |  URL | A fully qualified URL pointing to the location of a graphic file representing the brand for the service for use in dark mode applications.  File MUST be in SVG V1.1 format and MUST be either square or round.
 `brand_assets.color` <br/>*(added in v2.3)*  | OPTIONAL |  String |  Color used to represent the brand for the service expressed as a 6 digit hexadecimal color code in the form #000000.
 `terms_url` <br/>*(as of v3.0)* | OPTIONAL | Array&lt;Localized String&gt; | A fully qualified URL pointing to the terms of service (also often called "terms of use" or "terms and conditions") for the service.
-`terms_last_updated` <br/>*(added in v2.3)* | REQUIRED | Date | The date that the terms of service provided at `terms_url` were last updated. 
+`terms_last_updated` <br/>*(added in v2.3)* | Conditionally REQUIRED | Date | REQUIRED if `terms_url` is defined. The date that the terms of service provided at `terms_url` were last updated. 
 `privacy_url` <br/>*(as of v3.0)*| OPTIONAL | Array&lt;Localized String&gt; | A fully qualified URL pointing to the privacy policy for the service.
-`privacy_last_updated` <br/>*(added in v2.3)* | REQUIRED | Date | The date that the privacy policy provided at `privacy_url` was last updated. 
+`privacy_last_updated` <br/>*(added in v2.3)* | Conditionally REQUIRED | Date | REQUIRED if `privacy_url` is defined. The date that the privacy policy provided at `privacy_url` was last updated. 
 `rental_apps` | OPTIONAL | Object | Contains rental app information in the `android` and `ios` JSON objects.
 `rental_apps.android` | OPTIONAL | Object | Contains rental app download and app discovery information for the Android platform in the `store_uri` and `discovery_uri` fields. See [examples](#deep-links-examples) of how to use these fields and [supported analytics](#analytics).
 `rental_apps.android.store_uri`  | REQUIRED | URI | URI where the rental Android app can be downloaded from. Typically this will be a URI to an app store, such as Google Play. If the URI points to an app store, the URI SHOULD follow Android best practices so the viewing app can directly open the URI to the native app store app instead of a website.<br><br>See the [Analytics](#analytics) section for how viewing apps can report the origin of the deep link to rental apps. <br><br>Example value: `https://play.google.com/store/apps/details?id=com.example.android`