Align match-order schema with validation

Make the JSON Schema reject a match order unsupported by OBI.
Schema-based validators now fail before the CLI sees the configuration.

Author: MrAlias

devdocs/config/version-2.0/obi-extension.schema.json

@@ -480,11 +480,10 @@
         "match_order": {
           "type": "string",
           "enum": [
-            "first_match_wins",
-            "last_match_wins"
+            "first_match_wins"
           ],
           "default": "first_match_wins",
-          "description": "Rule evaluation order semantics.\nValues include: `first_match_wins`, `last_match_wins`.\nIf omitted, `first_match_wins` is used. `first_match_wins` requires exclude rules before include rules, and OBI does not support `last_match_wins`.\n"
+          "description": "Rule evaluation order semantics.\nThe supported value is `first_match_wins`.\nIf omitted, `first_match_wins` is used. Exclude rules must precede include rules.\n"
         },
         "poll_interval": {
           "type": "string",