Update stress-tester to use release/5.9-20230510

Author: shahmishal

utils/update_checkout/update-checkout-config.json

@@ -242,7 +242,7 @@
                 "swift-numerics": "1.0.1",
                 "swift-syntax": "release/5.9-20230510",
                 "swift-system": "1.1.1",
-                "swift-stress-tester": "release/5.9",
+                "swift-stress-tester": "release/5.9-20230510",
                 "swift-corelibs-xctest": "release/5.9",
                 "swift-corelibs-foundation": "release/5.9",
                 "swift-corelibs-libdispatch": "release/5.9",