docs: change install command to default to pfSense 2.8.0-RELEASE

Author: jaredhendrickson13

README.md

@@ -30,7 +30,7 @@ No need to create local users before authenticating.
 ## Installation 
 To install, simply run the following command from the pfSense command line:<br>
 ```
-pkg add https://github.com/jaredhendrickson13/pfsense-saml2-auth/releases/latest/download/pfSense-2.7-pkg-saml2-auth.pkg
+pkg add https://github.com/jaredhendrickson13/pfsense-saml2-auth/releases/latest/download/pfSense-2.8-pkg-saml2-auth.pkg
 ```
 
 To uninstall:<br>