Made a change to 'Path length on Finder Tabs' - I need to change it back to default
The unix command you used in terminal was the following:
defaults write com.apple.finder _FXShowPosixPathInTitle -bool YES

This adds a key to the Finder user defaults — _FXShowPosixPathInTitle — and sets it to true, which enables showing the full posix path of the file in the title bar. To turn that feature off and return to the original behavior, delete the key:
defaults delete com.apple.finder _FXShowPosixPathInTitle

For more information about using the defaults utility, see its man page. Once you delete the entry, it’s best to log out of your user from the Apple menu and then log back in to be sure the preference stuck.