graphics/qgis: Update to 3.16.1

Bugfix release [1][2].

[1] https://qgis.org/en/site/forusers/visualchangelog316/index.html
[2] https://github.com/qgis/QGIS/compare/final-3_16_0...final-3_16_1

If you miss features in QGIS that are actually built
into QGIS, you may need to enable additional options
in graphics/gdal, see pkg-message.

Approved by: arrowd (mentor)
Differential Revision: https://reviews.freebsd.org/D27374