Bug 2046584 - Remove getPreviousGeckoPrefStates from public NimbusClient API (#7412)

Author: freshstrangemusic

CHANGELOG.md

@@ -5,7 +5,7 @@
 ## Nimbus
 
 - Enrollment change events (visible to the UDL) now include the feature IDs of the features involved when possible. ([#7391](https://github.com/mozilla/application-services/pull/7391/))
-
+- Removed NimbusInterface.getPreviousGeckoPrefsState since it is unimplemented and the underlying SDK method is only used by tests. ([#7412](https://github.com/mozilla/application-services/pull/7412/))
 ## 🔧 What's Fixed 🔧
 
 ### Logins

components/nimbus/android/src/main/java/org/mozilla/experiments/nimbus/NimbusInterface.kt

@@ -208,16 +208,6 @@ interface NimbusInterface : FeaturesInterface, NimbusMessagingInterface, NimbusE
         geckoPrefStates: List<GeckoPrefState>,
     ) = Unit
 
-    /**
-     * Retrieves a list of previous states, if available, on an enrolled experiment, from a given slug.
-     *
-     * @param experimentSlug The slug of the experiment.
-     * @return The previous Gecko pref states of the given slug. Will return null if not available or invalid slug.
-     */
-    fun getPreviousGeckoPrefStates(
-        experimentSlug: String,
-    ): List<PreviousGeckoPrefState>? = null
-
     /**
      *  Reset internal state in response to application-level telemetry reset.
      *  Consumers should call this method when the user resets the telemetry state of the