devel/electron{32,34,35,36,37}: temporarily mark as BROKEN on i386

In pre-fetch target, a node process tries to fetch necessary node
modules for building the port. Currently on i386 platform, the process
stalls and eats up all available CPUs until it is killed, which is a
problem.

So temporarily mark electron ports as BROKEN on i386 platform until
the problem is solved.

PR: 270565
Reported by: antoine, pkg-fallout

(cherry picked from commit a5541c16e22dab9e19d1cad96f3be31c5941916f)