Remove errFn from getGroupMembers

Change-Id: I27b6be100b2a901f0a5b2bf4968a8e10c7e6a3d2
diff --git a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts
index 410140c..580a75c 100644
--- a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts
+++ b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts
@@ -537,16 +537,12 @@
     );
   }
 
-  getGroupMembers(
-    groupName: GroupId | GroupName,
-    errFn?: ErrorCallback
-  ): Promise<AccountInfo[] | undefined> {
+  getGroupMembers(groupName: GroupId | GroupName): Promise<AccountInfo[]> {
     const encodeName = encodeURIComponent(groupName);
-    return this._restApiHelper.fetchJSON({
+    return (this._restApiHelper.fetchJSON({
       url: `/groups/${encodeName}/members/`,
-      errFn,
       anonymizedUrl: '/groups/*/members',
-    }) as Promise<AccountInfo[] | undefined>;
+    }) as unknown) as Promise<AccountInfo[]>;
   }
 
   getIncludedGroup(
diff --git a/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts b/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts
index 8fc1935..8f11a60 100644
--- a/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts
+++ b/polygerrit-ui/app/services/services/gr-rest-api/gr-rest-api.ts
@@ -636,10 +636,7 @@
     errFn?: ErrorCallback
   ): Promise<GroupAuditEventInfo[] | undefined>;
 
-  getGroupMembers(
-    groupName: GroupId | GroupName,
-    errFn?: ErrorCallback
-  ): Promise<AccountInfo[] | undefined>;
+  getGroupMembers(groupName: GroupId | GroupName): Promise<AccountInfo[]>;
 
   getIncludedGroup(
     groupName: GroupId | GroupName