fix(tools/check_for_upgrade): Don't source profile

Reverts #2296, but mostly #1883.

There is no need to source ~/.profile when this script is read. oh-my-zsh writes no configuration data in ~/.profile.

If the user wishes to use data within ~/.profile, then they should source it in another place.

Fixes #2315
Merge pull request #3412 from mcornella/feltnerm-patch-1

Disable sourcing .profile when checking for available updates