Change Rvalid to Valid

Change all references to keywords like "Rvalid Values" to "Valid Values".
"Rvalid Values" has been deprecated.

Change-Id: I1b418fa69e5753c8bfb9e6a06a8b566359e10cae
Signed-off-by: Michael Walsh <micwalsh@us.ibm.com>
diff --git a/extended/run_keyword.py b/extended/run_keyword.py
index c2fe43b..3bb89c2 100644
--- a/extended/run_keyword.py
+++ b/extended/run_keyword.py
@@ -29,7 +29,7 @@
     Validate all program parameters.
     """
 
-    grv.rvalid_value("keyword_string")
+    grv.valid_value("keyword_string")
 
     return True