[BUGFIX] Tests: Remove unstable GeneralUtilityTest::getUrl*

Two tests check getUrl() by calling some resource on typo3.org.
This smells funny and the tests are unstable if network, dns
or typo3.org is down or slow. Mocking is not easily possible
with the lowlevel nature of getUrl().
The tests are removed for now.

Change-Id: I85a83345404c833a67c2f532e820fd28bb7c08e7
Resolves: #55821
Releases: 6.2, 6.1, 6.0
Reviewed-on: https://review.typo3.org/27518
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind