[opencascade] Update to 7.6.0

[Cheney-W]

• What does your PR fix?

  Fixes [opencascade] Bump version 7.5.0 -> 7.6.0 #21161

All features passed with following triplets:
x86-windows
x64-windows
x64-windows-static

[dg0yt]

For the record, this update causes the osg regression in vcpkg.ci.

From https://dev.opencascade.org/doc/overview/html/occt__upgrade.html#upgrade_occt760:

Poly_Triangulation does no more provide access to internal array structures: methods Nodes(), ChangeNode(), Triangles(), ChangeTriangle(), UVNodes(), ChangeUVNode(), Normals() have been removed. Methods of Poly_Triangulation for accessing individual nodal properties / triangles by index and implementing copy semantics should be used instead. The same is applicable to Poly_PolygonOnTriangulation interface.

osg regression:
D:\buildtrees\osg\src\raph-3.6.5-0028e69d98.clean\src\osgPlugins\OpenCASCADE\ReaderWriterOpenCASCADE.cpp(214,49): error C2039: 'Nodes': is not a member of 'Poly_Triangulation' [D:\buildtrees\osg\x64-windows-static-md-dbg\src\osgPlugins\OpenCASCADE\osgdb_opencascade.vcxproj]

Note that port osg doesn't have a port opencascade dependency. That's why it wasn't uncovered by CI.

This issue needs action in port osg. Maybe port osg has additional auto-detected dependencies. They must be control by vcpkg packaging.

[dg0yt]

This issue needs action in port osg. Maybe port osg has additional auto-detected dependencies. They must be control by vcpkg packaging.

Fixed in #21634.