Fullscreen scroll fix #15596 (#15621)

Scrolling gets disabled for the modal and then is supposed to be reenabled when modal is closed. However, SandboxedPortal eats the events that would tell the modal to go and do this. Do it on React lifecycle bits instead.

frontend/src/metabase/components/Modal.jsx

@@ -137,23 +137,20 @@ export class FullPageModal extends Component {
   }
 
   componentDidUpdate() {
+    if (!this.state.isOpen) {
+      document.body.style.overflow = "";
+    }
     this.setTopOfModalToBottomOfNav();
   }
 
   componentWillUnmount() {
     this._modalElement.parentNode.removeChild(this._modalElement);
+    document.body.style.overflow = "";
   }
 
   handleDismissal = () => {
     this.setState({ isOpen: false });
 
-    // restore scroll position and scrolling
-    document.body.style.overflow = "";
-    // On IE11 a timeout is required for the scroll to happen after the change of overflow setting
-    setTimeout(() => {
-      window.scrollTo(this._scrollX, this._scrollY);
-    }, 0);
-
     // wait for animations to complete before unmounting
     setTimeout(() => this.props.onClose && this.props.onClose(), 300);
   };

frontend/test/metabase/scenarios/dashboard/dashboard.cy.spec.js

@@ -743,7 +743,7 @@ describe("scenarios > dashboard", () => {
     });
   });
 
-  it.skip("should be possible to scroll vertically after fullscreen layer is closed (metabase#15596)", () => {
+  it("should be possible to scroll vertically after fullscreen layer is closed (metabase#15596)", () => {
     // Make this dashboard card extremely tall so that it spans outside of visible viewport
     cy.request("PUT", "/api/dashboard/1/cards", {
       cards: [