website: membus.slave is deprecated.

'slave' is now called 'cpu_side_ports', so we should update the doc to as same as the latest code.

Change-Id: Ieea1de5d7a45c20569bc8487e11b2af98a0e0a0d
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/59210
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Tested-by: Bobby Bruce <bbruce@ucdavis.edu>
diff --git a/_pages/documentation/learning_gem5/part1/part1_6_extending_configs.md b/_pages/documentation/learning_gem5/part1/part1_6_extending_configs.md
index 23e2a89..4901587 100644
--- a/_pages/documentation/learning_gem5/part1/part1_6_extending_configs.md
+++ b/_pages/documentation/learning_gem5/part1/part1_6_extending_configs.md
@@ -55,11 +55,11 @@
 
 ```
 system.cpu.createInterruptController()
-#system.cpu.interrupts[0].pio = system.membus.master
-#system.cpu.interrupts[0].int_master = system.membus.slave
-#system.cpu.interrupts[0].int_slave = system.membus.master
+#system.cpu.interrupts[0].pio = system.membus.mem_side_ports
+#system.cpu.interrupts[0].int_requestor = system.membus.cpu_side_ports
+#system.cpu.interrupts[0].int_responder = system.membus.mem_side_ports
 
-system.system_port = system.membus.slave
+system.system_port = system.membus.cpu_side_ports
 ```
 
 You can either delete or comment them out as above. Next let's set