Update WMR package number

Author: keveleigh

Packages/manifest.json

@@ -6,7 +6,7 @@
     "com.unity.xr.arfoundation": "1.5.0-preview.6",
     "com.unity.xr.arkit": "2.1.2",
     "com.unity.xr.openvr.standalone": "1.0.5",
-    "com.unity.xr.windowsmr.metro": "1.0.15",
+    "com.unity.xr.windowsmr.metro": "1.0.18",
     "com.unity.modules.ai": "1.0.0",
     "com.unity.modules.animation": "1.0.0",
     "com.unity.modules.assetbundle": "1.0.0",