depends: Drop workaround for a fixed bug in Qt build system

Summary:
The bug reports:

• https://bugreports.qt.io/browse/QTBUG-35444
• https://bugreports.qt.io/browse/QTBUG-32519

Fixed in Qt 5.3.0 (the workaround was introduced for Qt 5.2.1).

This is a backport of core#20650

Depends on D13662

Test Plan: gitian builds

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13664