fix: remove padding on popovers of newly-created fields (#2268)

frontend/appflowy_flutter/lib/plugins/database_view/grid/presentation/widgets/header/grid_header.dart

@@ -186,6 +186,7 @@ class CreateFieldButton extends StatelessWidget {
     return AppFlowyPopover(
       direction: PopoverDirection.bottomWithRightAligned,
       asBarrier: true,
+      margin: EdgeInsets.zero,
       constraints: BoxConstraints.loose(const Size(240, 600)),
       child: FlowyButton(
         radius: BorderRadius.zero,

frontend/appflowy_flutter/lib/plugins/database_view/widgets/row/row_detail.dart

@@ -206,6 +206,7 @@ class _CreatePropertyButtonState extends State<_CreatePropertyButton> {
       constraints: BoxConstraints.loose(const Size(240, 200)),
       controller: popoverController,
       direction: PopoverDirection.topWithLeftAligned,
+      margin: EdgeInsets.zero,
       onClose: widget.onClosed,
       child: Container(
         height: 40,