You can uninstall Save Game Pro manually or automatically using General Settings window.
You can uninstall Save Game Pro automatically by a single click, by Going to Window > Save Game Pro > General Settings:
Now, go to General Operations section and click Uninstall Save Game Pro:
And click Yes, Uninstall button to confirm and uninstall Save Game Pro completely:
Just Remove BayatGames/SaveGamePro folder to remove all Save Game Pro files and then go to Player Settings and remove Save Game Pro define symbols.