(core) Fix test util and upgrade fixtures

Summary:
Fixes a test util that broke after a sync with grist-core, and upgrades
fixtures after a migration was added.

Test Plan: N/A

Reviewers: paulfitz

Reviewed By: paulfitz

Subscribers: paulfitz

Differential Revision: https://phab.getgrist.com/D3810

app/common/ThemePrefs-ti.ts

@@ -296,6 +296,9 @@ export const ThemeColors = t.iface([], {
   "menu-toggle-active-fg": "string",
   "menu-toggle-bg": "string",
   "menu-toggle-border": "string",
+  "info-button-fg": "string",
+  "info-button-hover-fg": "string",
+  "info-button-active-fg": "string",
   "button-group-fg": "string",
   "button-group-light-fg": "string",
   "button-group-bg": "string",