Fix <return> method doc for IsFeatureEnabled (#329)

Author: mikechu-optimizely

OptimizelySDK/Optimizely.cs

@@ -447,8 +447,10 @@ public Variation GetForcedVariation(string experimentKey, string userId)
         /// <param name="featureKey">The feature key</param>
         /// <param name="userId">The user ID</param>
         /// <param name="userAttributes">The user's attributes.</param>
-        /// <returns>True if feature is enabled, false or null otherwise</returns>
-        public virtual bool IsFeatureEnabled(string featureKey, string userId, UserAttributes userAttributes = null)
+        /// <returns>True if feature is enabled, otherwise false</returns>
+        public virtual bool IsFeatureEnabled(string featureKey, string userId,
+            UserAttributes userAttributes = null
+        )
         {
             var config = ProjectConfigManager?.GetConfig();