Fix flaking collection tests [ci skip] (#21417)

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

@@ -261,8 +261,12 @@ describe("scenarios > collection_defaults", () => {
 
       it("should see a child collection in a sidebar even with revoked access to its parent (metabase#14114)", () => {
         cy.visit("/");
-        cy.findByText("Child");
-        cy.findByText("Parent").should("not.exist");
+
+        cy.get("main").within(() => {
+          cy.findByText("Child");
+          cy.findByText("Parent").should("not.exist");
+        });
+
         cy.findByText("Browse all items").click();
 
         navigationSidebar().within(() => {
@@ -554,7 +558,7 @@ describe("scenarios > collection_defaults", () => {
 
       cy.visit("/");
       // There is already a collection named "First collection" in the default snapshot
-      cy.findByText("First collection");
+      cy.get("main").findByText("First collection");
     });
   });
 });