Update nightly.steps.yaml (#270)

Author: simonsarginson

.buildkite/nightly.steps.yaml

@@ -12,8 +12,8 @@ steps:
       message: "exampleproject-4.26 ${BUILDKITE_MESSAGE}"
       env: 
         BUILD_TYPE: "EXAMPLE"
-        GDK_BRANCH: "${GDK_BRANCH:-0.13.0-rc}" # NOTE: temp fix for new ci release interop issues
-        ENGINE_BRANCH: "${ENGINE_BRANCH:-4.26-SpatialOSUnrealGDK-0.13.0-rc}" # NOTE: temp fix for new ci release interop issues
+        GDK_BRANCH: "${GDK_BRANCH:-0.13.0}" # NOTE: temp fix for new ci release interop issues
+        ENGINE_BRANCH: "${ENGINE_BRANCH:-4.26-SpatialOSUnrealGDK-0.13.0}" # NOTE: temp fix for new ci release interop issues
         ENGINE_MAJOR: "4.26"
         PROJECT_BRANCH: "${BUILDKITE_BRANCH}"
         USE_FASTBUILD: "True"