chore: disable StructuredQueriesPostgresSQLValidation trait by default

SQL validation requires PostgresNIO which pulls in entire NIO stack.
Disable by default to keep CI builds fast and dependency tree light.

To enable SQL validation locally:
1. Uncomment 'StructuredQueriesPostgresSQLValidation' in .default(enabledTraits:)
2. Run: swift test

Author: coenttb

Package.swift

@@ -53,7 +53,7 @@ let package = Package(
             enabledTraits: [
                 "StructuredQueriesPostgresCasePaths",
 //                "StructuredQueriesPostgresTagged",
-                "StructuredQueriesPostgresSQLValidation",
+//                "StructuredQueriesPostgresSQLValidation",
             ]
         ),
     ],