[Android] Pin Screen flickering on biometry request

[tuliomir]

On Android, when the user configures the app to use fingerprint biometry, the PinScreen digits still show, causing confusion about the expected input.

To reproduce this issue:

• Configure the app to use biometry
• Close the app
• Open it again
• The biometry is requested against a blank, gray screen

Notice the pin digits are shown for a period of time before the "Loading Wallet History" screen is displayed. This period may be longer or shorter according to the backend response time.

Below, a sample video shows the behavior. Note that on this video the background was painted blue to showcase another behavior that is unrelated to this issue and may be ignored in this scope. The flicker happens at 0:08 seconds.

decide.screen-2023-10-26_20.02.25.mp4