Drop support for Okteta < 0.26.0 (Kasten 0.4.0)
0.26.0 was released a year (11 March 2019) before the current min Qt 5.15.2 version (20 Nov 2020), so can be assumed to always be present, thus no more need for older compat code.
0.26.0 was released a year (11 March 2019) before the current min Qt 5.15.2 version (20 Nov 2020), so can be assumed to always be present, thus no more need for older compat code.