message: Add `useAcrylicInTabRow` to JSON schema
  `useAcrylicInTabRow` was missing from the JSON schema, so I added it in.
  ## References
  ## PR Checklist
  * [x] Closes
  * [x] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
  * [x] Schema updated.
diff: "default": "false",
  "description": "When set to true, the Terminal's tray icon will always be shown in the system tray.",
  "type": "boolean"
  + },
  + "useAcrylicInTabRow": {
  + "default": "false",
  + "description": "When set to true, the tab row will have an acrylic background with 50% opacity.",
  + "type": "boolean"
  },
  "actions": {
  "description": "Properties are specific to each custom action.",
  