symbols/se: remove a variant that does not differ from its parent

The "rus_nodeadkeys" variant included se(nodeadkeys), but then it also included se(rus) which includes se(basic) which overwrites all the non-dead symbols with dead symbols again.

In the eighteen years that these Russian variants existed no one has complained about the dead keys in the "rus_nodeadkeys" variant, so... just delete it, as it is identical to the "rus" variant.