Howdy elh0ff0_vi,
Thanks for posting in the Apple Support Communities.
We understand you're noticing a change with using an apostrophe in the Notes app, so let's see if we can help to isolate this with you. For starters, we would recommend confirming you have the latest available macOS version installed on your MacBook Air. If an update is available, be sure to backup your information before installing this to be safe. Take a look at the steps below for assistance with checking for an update, and you can find steps to back up here: How to back up your Mac - Official Apple Support
Keep your Mac up to date - Apple Support
Check for updates manually
To install updates manually on your Mac, do one of the following:
• To download macOS software updates, choose Apple menu 
> System Settings, click General 
in the sidebar (you may need to scroll down), then click Software Update on the right.
• To update software downloaded from the App Store, click the Apple menu—the number of available updates, if any, is shown next to App Store. Choose App Store to continue in the App Store 
app.
If you have the latest updates installed, let's check to see if you may have installed new fonts that could be related to this. For assistance with checking fonts on your Mac to remove, take a look at this resource: Install or remove fonts on your Mac - Apple Support
Should that not help, let us know if the same happens on a new test admin user with your MacBook Air. To complete this process, check out : Set up users, guests, and groups on Mac - Apple Support This will help to determine if it's isolated to your user account or not, to move forward.
Have a great day!
