Don't force completion recalculation in icomplete-fido-ret

Don't force completion recalculation in icomplete-fido-ret

Besides the adverse effect of delaying completions, it tripped up the
useful logic of icomplete-force-complete-and-exit in the case where a
default was available, but no completions calculated yet.

* lisp/icomplete.el (icomplete-fido-ret): Don't force calculation
of completions.