At the top left of the screen, select the ‘Edit’ menu >> ‘Editor Preferences’ >> ‘Keyboard shortcuts’ tab on the left >> Under General Keyboard Shortcuts, search for the 'Play World (PIE/SIE) drop down (or type ‘stop’ in the search), in there you will find a ‘Stop stop simulation’ key input. You can change or delete this key input.
Edit (2024): This method works for both Unreal Engine 4 & 5.