We are unable to ping the the PC2 because router 2 does not know how to reach network 192.168.3.0.
you can check the routing table that router 2 do not have any route learned through rip protocol.
Although we have enabled the protocol on both routers and we have advertised the 192.168.3.0 network but
we are unable to reach and ping the network.
Network command does two things
1. It advertise the network 
2. It enable to interface to receive and send RIP advertisements 

In this case as we have not advitised the 192.168.2.0 on router 2 so Rip protocol is not enabled on
fastethernet0/1 interface
As this interface is the one connected to the other router hence both routers are unable to receive routing 
updates

Advertise 192.168.2.0 network on router 3 and you will be able to ping the PC2 from PC0 and you will see the 
routes learned though RIP protocol on both routers.