cypress: Raise vis wait time, and tweak expect error text

Recent refactoring slightly changed the wording of an error message,
which was tripping up the Cypress tests.  Also raised the cy.wait()
delay time in one set of tests, as the previous value was low
enough that it sometimes caused test failures on my dev setup.

cypress/e2e/1-webui/live_visualisation.cy.js

@@ -274,7 +274,7 @@ describe('live visualisation', () => {
 
     // Try accessing a private database's visualisation page
     cy.visit({url: '/vis/default/Join Testing with index.sqlite', failOnStatusCode: false})
-    cy.get('[data-cy="errormsg"').should('contain', 'doesn\'t seem to exist')
+    cy.get('[data-cy="errormsg"').should('contain', 'doesn\'t exist')
 
     // Switch back to the default user
     cy.request('/x/test/switchdefault')

cypress/e2e/1-webui/visualisation.cy.js

@@ -1,7 +1,7 @@
 import path from "path";
 
 // Sometimes we need a delay between making a change, and testing it, otherwise the AngularJS changes are missed
-let waitTime = 150;
+let waitTime = 250;
 
 // TODO: Test that when provided a commit id, we visualise the data for that commit rather than the latest commit
 
@@ -290,7 +290,7 @@ describe('visualisation', () => {
 
     // Try accessing a private database's visualisation page
     cy.visit({url: '/vis/default/Assembly Election 2017 with view.sqlite', failOnStatusCode: false})
-    cy.get('[data-cy="errormsg"').should('contain', 'doesn\'t seem to exist')
+    cy.get('[data-cy="errormsg"').should('contain', 'doesn\'t exist')
 
     // Switch back to the default user
     cy.request('/x/test/switchdefault')