build: bump to rxjs 6.0 final (#11002)

Bumps to the stable version of rxjs 6.0.

Author: crisbeto

package-lock.json

@@ -33,7 +33,7 @@
     "@angular/forms": "6.0.0-rc.5",
     "@angular/platform-browser": "6.0.0-rc.5",
     "core-js": "^2.4.1",
-    "rxjs": "6.0.0-uncanny-rc.7",
+    "rxjs": "6.0.0",
     "systemjs": "0.19.43",
     "tsickle": "^0.27.2",
     "tslib": "^1.9.0",