Windows: Fix warnings about being unable to load fonts from font dir.

Do not call QPlatformFontDatabase::populateFontDatabase(), which
tries to load qpf2-fonts from the Qt library directory.
This directory is not installed on Windows.

Note: This affects non-in-source builds only.

Task-number: QTBUG-26066
Change-Id: I5782e61965958fc48e0edd7a3d50eef325529708
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

src/plugins/platforms/windows/qwindowsfontdatabase.cpp

@@ -1075,7 +1075,6 @@ void QWindowsFontDatabase::populateFontDatabase()
 {
     m_families.clear();
     removeApplicationFonts();
-    QPlatformFontDatabase::populateFontDatabase();
     populate(); // Called multiple times.
     // Work around EnumFontFamiliesEx() not listing the system font, see below.
     const QString sysFontFamily = QGuiApplication::font().family();

src/plugins/platforms/windows/qwindowsfontdatabase_ft.cpp

@@ -278,7 +278,6 @@ static int CALLBACK storeFont(ENUMLOGFONTEX* f, NEWTEXTMETRICEX *textmetric,
 void QWindowsFontDatabaseFT::populateFontDatabase()
 {
     m_families.clear();
-    QPlatformFontDatabase::populateFontDatabase();
     populate(); // Called multiple times.
     // Work around EnumFontFamiliesEx() not listing the system font, see below.
     const QString sysFontFamily = QGuiApplication::font().family();