Time-series chart E2E tests: ensure that the chart is ready first (#19969)

frontend/test/metabase/scenarios/binning/correctness/time-series.cy.spec.js

@@ -169,9 +169,11 @@ function getVisualization(binningType) {
 
 function assertOnXYAxisLabels() {
   cy.get(".y-axis-label")
+    .should("be.visible")
     .invoke("text")
     .should("eq", "Count");
   cy.get(".x-axis-label")
+    .should("be.visible")
     .invoke("text")
     .should("eq", "Created At");
 }