fix(specs): Add Contest Parameters to System Parameters cluster in defs.cue

- Add Contest Parameters to System Parameters docs array
- Update comment to reflect that Contest Parameters are included
- Aligns CUE definition with signed_doc.json specification
- Fixes inconsistency where JSON included Contest Parameters but CUE excluded it

Author: nathanbogale

specs/definitions/signed_doc_types/defs.cue

@@ -38,12 +38,13 @@ allDocNames: [...#docName] & [
 #DocClusters: [string]: #DocumentCluster
 
 doc_clusters: #DocClusters & {
-	// System parameters define the system, excludes Contests.
+	// System parameters define the system hierarchy.
 	"System Parameters": {
 		docs: [
 			"Brand Parameters",
 			"Campaign Parameters",
 			"Category Parameters",
+			"Contest Parameters",
 		]
 	}
 }