Fix bug where stale data is shown in custom css drawer when changing components

packages/builder/src/components/design/PropertiesPanel/CustomStylesSection.svelte

@@ -35,7 +35,8 @@
     <ActionButton on:click={openDrawer}>Edit custom CSS</ActionButton>
   </div>
 </DetailSummary>
-<Drawer bind:this={drawer} title="Custom CSS">
+{#key componentInstance?._id}
+  <Drawer bind:this={drawer} title="Custom CSS">
     <Button cta slot="buttons" on:click={save}>Save</Button>
     <DrawerContent slot="body">
       <div class="content">
@@ -45,7 +46,8 @@
         </Layout>
       </div>
     </DrawerContent>
-</Drawer>
+  </Drawer>
+{/key}
 
 <style>
   .content {