(core) Remove the aclUI=1 flag and add 'BETA' tag to the Access Rules page name.

Summary:
- Remove support for aclUI=1 URL parameter, making it the default.
- Add 'BETA' tag to the Access Rules link in side panel.
- Remove all mentions of aclUI=1 in tests.

Test Plan: Updated tests should pass

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2766

app/client/ui/LeftPanelCommon.ts

@@ -105,8 +105,8 @@ export const cssPageEntry = styled('div', `
   }
   &-disabled, &-disabled:hover, &-disabled.weasel-popup-open {
     background-color: initial;
-    color: ${colors.mediumGrey};
-    --icon-color: ${colors.mediumGrey};
+    color: ${colors.darkGrey};
+    --icon-color: ${colors.darkGrey};
   }
   .${cssTools.className}-collapsed > & {
     margin-right: 0;