Improve the expired page error message

When the Android device does not support Custom Tabs, the default browser is used in the authentication flow. The flow can finish normally, however, a tab is left unclosed in the default browser. When the user refresh the unclosed page, they will see the expired page error message.

We would like to improve the error message such that the user understands that the expiration is expected and they can close the page.

The improved error message cannot be too specific for this case because the same error message is also used for expired pages that have been idling for a long time.

Suggestion: "The page has expired. You can either close this page, or retry your request."

No file or test is named. Start by locating the expired-page message used in the authentication flow, then verify the revised wording covers both the unclosed Android browser page and long-idle expired pages; done means the message clearly offers closing or retrying.

Written by the indexing model from the issue text.