fix: remove valid enum values from CE7247 reserved word list

The keyword-as-identifier.mdl regression test (added in 3e7d2d7) uses
Empty, Object, Owner, and Type as enumeration values. Mendix accepts
these via mx check, but our executor rejected them with CE7247, failing
TestMxCheck_DoctypeScripts on CI.

Removes empty/object/owner/type from mendixReservedWords. Remaining
Mendix-specific entries (changedby, changeddate, con, context,
createddate, currentuser, guid, id, mendixobject, submetaobjectname)
are not exercised by the test and may still be genuinely reserved.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ako

mdl/executor/cmd_enumerations.go

@@ -248,9 +248,8 @@ var mendixReservedWords = map[string]bool{
 	"while": true,
 	// Mendix-specific reserved identifiers
 	"changedby": true, "changeddate": true, "con": true, "context": true,
-	"createddate": true, "currentuser": true, "empty": true, "guid": true,
-	"id": true, "mendixobject": true, "object": true, "owner": true,
-	"submetaobjectname": true, "type": true,
+	"createddate": true, "currentuser": true, "guid": true,
+	"id": true, "mendixobject": true, "submetaobjectname": true,
 }
 
 // ValidateEnumeration checks enumeration value names for reserved words.