Update to preview-6 (#235)

Author: ImprobableMatthew

.buildkite/nightly.steps.yaml

@@ -37,7 +37,7 @@ env:
     GDK_REPOSITORY: "[email protected]:spatialos/UnrealGDK.git"
     MAIN_MAP_NAME: "Control_Small"
     SPATIAL_PROJECT_NAME: "unreal_gdk"
-    SPATIAL_RUNTIME_VERSION: "15.0.0-preview-5" ## the runtime version of SpatialOS
+    SPATIAL_RUNTIME_VERSION: "15.0.0-preview-6" ## the runtime version of SpatialOS
 
 steps:
   - label: "generate-pipeline-steps"

spatial/spatialos.json

@@ -1,11 +1,11 @@
 {
   "name": "your_project_name_here",
   "project_version": "0.0.1",
-  "sdk_version": "15.0.0-preview-5",
+  "sdk_version": "15.0.0-preview-6",
   "dependencies": [
     {
       "name": "standard_library",
-      "version": "15.0.0-preview-5"
+      "version": "15.0.0-preview-6"
     }
   ]
 }