[request] waitVanish/onVanish should run with a default minimum similarity near 1.0

Usually the intention of the user, when using waitVanish/onVanish, is to wait for a specific image to vanish.

This image usually is matched with a high similarity score (above 0.9 to 0.95).

If these methods work with the standard similarity of 0.7, the risk is high, that something is found on the screen, that is not intended, if the object has already vanished, with the consequence, that the script might hang.

The average user might not be aware of this situation, so it is a convenience to let these methods use e.g. 0.95 as standard.

Currently you have to specify a pattern with similarity set to an appropriate high value, to avoid these situations.