I see. So, if you go to Platform, then Variables, you can create a new variable that is Secret (rather than Simple). Secret variables are only accessible by PSU itself and are encrypted. Your script could simply be modified to reference the variable for those lines. This would then allow you to avoid having sensitive information stored within the script directly (as well as being able to reuse the variable in other scripts if needed).
For example, it would change to something like $headers2.Add("X-Cisco-Meraki-API-Key", $($Secret:apikeyvariable))