As always, you can change the Google Classroom code in the settings of your class. Click on the settings cog in the upper right.
The General section of the settings is now updated to allow you to use a LINK to invite students to the class. To accommodate this the “Reset” option moved. It is no longer next to the code.
Manage Invite Codes
The default for “Manage invite codes” is “Enabled.” If you click on the tiny triangle next to “Enabled” you will see the option to “Reset” the code.