[MM-59825] Fix linter error found by updated govet (#27715)

server/channels/app/channel_bookmark_test.go

@@ -486,13 +486,13 @@ func TestUpdateChannelBookmarkSortOrder(t *testing.T) {
 
 	t.Run("change order of bookmarks error when new index is out of bounds", func(t *testing.T) {
 		_, appErr = th.App.UpdateChannelBookmarkSortOrder(bookmark3.Id, channelId, int64(-1), "")
-		assert.Error(t, appErr)
+		assert.NotNil(t, appErr)
 		_, appErr = th.App.UpdateChannelBookmarkSortOrder(bookmark3.Id, channelId, int64(5), "")
-		assert.Error(t, appErr)
+		assert.NotNil(t, appErr)
 	})
 
 	t.Run("change order of bookmarks error when bookmark not found", func(t *testing.T) {
 		_, appErr = th.App.UpdateChannelBookmarkSortOrder(model.NewId(), channelId, int64(0), "")
-		assert.Error(t, appErr)
+		assert.NotNil(t, appErr)
 	})
 }