precompilepkgs: don't confuse single package in project with requesting single package (#53865)
Followup to https://github.com/JuliaLang/julia/pull/53653
Separate from #53862 because this one is just broken on master
Without this if you precompile a project with a single dep it thought
the user was calling `precompile Dep` or `using Dep` so went into live
print mode, which is confusing.