misc: bump QML modules versions to x.15

src/mainview/components/InitialCallPage.qml

src/mainview/components/InvitationView.qml

src/mainview/components/MainOverlay.qml

src/mainview/components/MessageBar.qml

src/mainview/components/MessageBarTextArea.qml

src/mainview/components/MessageWebView.qml

src/mainview/components/MessageWebViewFooter.qml

src/mainview/components/MessageWebViewHeader.qml

src/mainview/components/OngoingCallPage.qml

src/mainview/components/ParticipantCallInStatusDelegate.qml

src/mainview/components/ParticipantCallInStatusView.qml

src/mainview/components/ParticipantControlLayout.qml

src/mainview/components/ParticipantOverlay.qml

src/mainview/components/ParticipantOverlayButton.qml

src/mainview/components/ParticipantOverlayMenu.qml

src/mainview/components/ParticipantsLayer.qml

src/mainview/components/PluginHandlerItemDelegate.qml

src/mainview/components/PluginHandlerPicker.qml

src/mainview/components/ProjectCreditsScrollView.qml

src/mainview/components/ReadOnlyFooter.qml