Fix GUID of generic polypropylene

The GUID that was listed turned out to be the Ultimaker-brand polypropylene. I've generated this GUID myself using Python's uuid.uuid4(). This GUID is not used in any spools or whatsoever anyway.

Contributes to issue CURA-3960.

generic_polypropylene.xml.fdm_material

@@ -9,7 +9,7 @@ Generic Polypropylene profile. Serves as an example file, data in this file is n
             <material>Polypropylene</material>
             <color>Generic</color>
         </name>
-        <GUID>c7005925-2a41-4280-8cdd-4029e3fe5253</GUID>
+        <GUID>aa22e9c7-421f-4745-afc2-81851694394a</GUID>
         <version>0</version>
         <description />
         <adhesion_info />