Remove Kirigami.Units.gridUnit * 16 maximum width restriction on
providerAccountLabel in ProviderHeader.qml so provider account text (e.g. email)
can expand to its full implicit width when popup space is available, while
retaining Layout.fillWidth and Layout.minimumWidth for responsive middle-elision
on narrow popups.

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Co-authored-by: Lucenx9 <185146821+Lucenx9@users.noreply.github.com>