Fix out of date validator instructions

Redfish service validator has been a properly installable package
since[1]

Update the instructions to make it trivial to install and use.

[1] https://github.com/DMTF/Redfish-Service-Validator/commit/51d4c0dddc0fc5a3697839bf0683f965a9464941

Change-Id: Ib94a7983e5cf2759561205c44549cf144d26a61e
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/TESTING.md b/TESTING.md
index 2847214..111d61a 100644
--- a/TESTING.md
+++ b/TESTING.md
@@ -129,10 +129,10 @@
 must run on real hardware since the resource tree will be more complete.
 
 ```bash
-$ git clone https://github.com/DMTF/Redfish-Service-Validator.git
+sudo pip3 install redfish_service_validator
 
 # run validator and inspect the report for failures
-$ python3 RedfishServiceValidator.py \
+rf_service_validator \
   --auth Session -i https://1.2.3.4:443 \
   -u root -p 0penBmc
 ```