fix: some UI issues

Author: asjqkkkk

frontend/appflowy_flutter/lib/plugins/document/presentation/editor_plugins/link_embed/link_embed_menu.dart

@@ -69,7 +69,7 @@ class _LinkEmbedMenuState extends State<LinkEmbedMenu> {
     return Container(
       padding: EdgeInsets.all(4),
       decoration: BoxDecoration(
-        borderRadius: BorderRadius.circular(16),
+        borderRadius: BorderRadius.circular(12),
         color: fillScheme.primaryAlpha80,
       ),
       child: Row(

frontend/appflowy_flutter/lib/plugins/document/presentation/editor_plugins/link_preview/custom_link_preview.dart

@@ -73,7 +73,7 @@ class CustomLinkPreviewWidget extends StatelessWidget {
             buildImage(context),
             Expanded(
               child: Padding(
-                padding: const EdgeInsets.fromLTRB(20, 12, 60, 12),
+                padding: const EdgeInsets.fromLTRB(20, 12, 58, 12),
                 child: status != LinkLoadingStatus.idle
                     ? buildLoadingOrErrorWidget()
                     : Column(

frontend/appflowy_flutter/lib/plugins/document/presentation/editor_plugins/link_preview/custom_link_preview_block_component.dart

@@ -150,8 +150,8 @@ class CustomLinkPreviewBlockComponentState
         child,
         if (showActions)
           Positioned(
-            top: 16,
-            right: 16,
+            top: 12,
+            right: 12,
             child: CustomLinkPreviewMenu(
               onMenuShowed: () {
                 isMenuShowing = true;