science/elmerfem: Drop unused Qt5 deps

Remove DEPRECATED/EXPIRATION_DATE. This port does not need the
deprecated Qt5 WebKit module. There is no reference to it anywhere in
the code.

Maintainer reckons these were leftover indirect dependencies from
math/vtk6.

PR: 275532
Approved by: Henrik Gulbrandsen <henrik@gulbra.net> (maintainer)