Extend timeout to deflake test

CaptivePortalLoginActivity may load the page slowly in lower
performance devices. Test expects the login page to be loaded
within 10s. The flaky happened sometimes since loading page
took 10+ seconds and failed the test.

Extend the timeout from 10s to 20s to deflake the test.

Bug: 225800341
Test: atest CaptivePortalTest
Change-Id: I98ab3dbc78cb95eeee95d1c86ab286600c98390b
1 file changed