Render Workbench maintainer stepping down

[luzpaz]

Render WB maintainer, @howetuft, has stepped down from maintainership.

source: FreeCAD/FreeCAD-render@770dffd

We really appreciate all the amazing work done to the Render WB since howetuft took up the mantle.

Stating the obvious but a new maintainer will need to be vetted since this is a popular and integral addon.

cc @chennes