qTox does not build on Debian 8 Jessie because of QVector<T>::removeOne() usage

[Talkless]

Brief Description

OS: Debian 8 KDE
qTox version: HEAD
toxcore: HEAD
Qt: 5.3.2, stock Debian 8
Hardware: VirtualBox

Reproducible: Always

Steps to reproduce

Build qTox using stock Qt on Debian 8

Observed Behavior

src/widget/passwordedit.cpp: In member function ‘void PasswordEdit::unregisterHandler()’:
src/widget/passwordedit.cpp:47:31: error: ‘class QVector<QAction*>’ has no member named ‘removeOne’
         eventHandler->actions.removeOne(action);
                               ^

As removeOne() was added in Qt 5.4

Expected Behavior

Should build on all supported systems, mentioned on INSTALL.md.

I believe it should be stressed in contribution guidelines to use lowest-common-denominator Qt version. This is not the first time I have reported such incompatibility error.

[Talkless]

There are two usages of removeOne():
https://github.com/tux3/qTox/search?utf8=%E2%9C%93&q=removeOne

[Talkless]

I'm working on a fix.

[Talkless]

Second removeOne() was actually with QList<> which is OK. Only one file had to be changed.