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

tools/check_for_upgrade.sh

@@ -22,8 +22,6 @@ if [[ -z "$epoch_target" ]]; then
   epoch_target=13
 fi
 
-[ -f ~/.profile ] && source ~/.profile
-
 # Cancel upgrade if the current user doesn't have write permissions for the
 # oh-my-zsh directory.
 [[ -w "$ZSH" ]] || return 0