[Sketcher] Delete check for OCC >= 6.9.0

[AjinkyaDahale]

The oldest version we plan to support is 7.0.0 (which comes with Ubuntu 20.04).

See https://forum.freecadweb.org/viewtopic.php?f=10&p=650487#p650487.

[luzpaz]

This likely also won't be an issue since most of the package ecosystem has moved to >=7.2.0 (https://repology.org/project/opencascade-occt/badges)

[AjinkyaDahale]

@luzpaz that is true, but currently an important library has been removed, which makes the join operation fail (see linked post). We should either merge #8103 or this one (or both).

[luzpaz]

@donovaly removed the header in question it looks like.

[AjinkyaDahale]

@wwmayer tagging you as well since we are talking about it in that forum thread.

[freecadci]

for feature branch PR_8106. Pipeline 735666308 was triggered at 8ec4bd1. All CI branches and pipelines.

[freecadci]

for feature branch PR_8106. Pipeline 735722690 was triggered at 8ec4bd1. All CI branches and pipelines.