don't concatenate to etc/julia/juliarc.jl in make dist

This is already concatenated into as a prerequisite of `make release`,
and copied over by `make install` on line 235. There are 2 copies of
the `let user_data_dir` block in the distribution folder.
Merge pull request #7440 from tkelman/patch-6

Windows: don't concatenate to etc/julia/juliarc.jl in make dist