Revert "disable filteraudio, because it makes audio quality worse"

This reverts commit 17f13459b6.

src/widget/form/settings/avform.cpp

@@ -46,16 +46,13 @@ AVForm::AVForm() :
 
     bodyUI->btnPlayTestSound->setToolTip(
                 tr("Play a test sound while changing the output volume."));
+
 #ifdef QTOX_FILTER_AUDIO
     bodyUI->filterAudio->setChecked(Settings::getInstance().getFilterAudio());
 #else
     bodyUI->filterAudio->setDisabled(true);
 #endif
 
-    // temporary remove audio filtering, because it makes audio quality worse
-    Settings::getInstance().setFilterAudio(false);
-    bodyUI->filterAudio->hide();
-
     auto qcbxIndexChangedStr = (void(QComboBox::*)(const QString&)) &QComboBox::currentIndexChanged;
     auto qcbxIndexChangedInt = (void(QComboBox::*)(int)) &QComboBox::currentIndexChanged;
     connect(bodyUI->inDevCombobox, qcbxIndexChangedStr, this, &AVForm::onInDevChanged);