As @ammahend stated, the Meraki AP does not have any control over the endpoint. If the endpoint has the SSID endpoint configured on it, it may have the ability to share or show that password in plain text.
You can prevent this by either:
- Managing the endpoint through MDM software (such as Meraki Systems Manager or MS Intune)
- Using an authentication mechanism that doesn't use pre-shared keys - such as certificate authentication