(core) Skip saving layout resizes in read-only mode

Summary:
This change causes a notification about missing
write access to no longer be shown when resizing layouts
as a viewer.

Test Plan: Browser test.

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D3167

app/client/components/ViewLayout.ts

@@ -106,7 +106,11 @@ export class ViewLayout extends DisposableWithEvents implements IDomComponent {
       this._isResizing.set(false);
       layoutSaveDelay.schedule(1000, () => {
         if (!this._layout) { return; }
-        (this.viewModel.layoutSpecObj as any).setAndSave(this._layout.getLayoutSpec());
+
+        // Only save layout changes when the document isn't read-only.
+        if (!this.gristDoc.isReadonly.get()) {
+          (this.viewModel.layoutSpecObj as any).setAndSave(this._layout.getLayoutSpec());
+        }
         this._onResize();
       });
     });