Fix previous gitignore change for uvm directory rejig
Fix previous gitignore change for uvm directory rejig

I'd written the original patch (b157573) on a branch that didn't
include commit 2431551 (which moves stuff that was in dv/uvm into
dv/uvm/core_ibex). Apparently, I'd fixed up the rule for the output
directory, but I'd missed the ucli.key file.

AmbiML/ibex,AmbiML/ibex,AmbiML/ibex,lowRISC/ibex,lowRISC/ibex,lowRISC/ibex,lowRISC/ibex,AmbiML/ibex