poppler: Update to 21.05.0

poppler: Update to 21.05.0

- Update from 21.04.0 to 21.05.0
- Update of rootfile
- Ran find-dependencies - nothing found
- Changelog
   Release 21.05.0:
      core:
         * Fix crashes in malformed files
         * Export SplashFont* symbols used by Scribus
         * Minor code improvements
      glib:
         * Enhance find to support multi-line matching
      qt5/qt6:
         * Make sure new signatures are always properly oriented
         * Allow to pass the border width when signing
      utils:
         * pdftoppm: Fix regression when using single scaleTo. Issue #1062
      build system:
         * Allow to disable building manual tests

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>