Update Mockttp for assorted small fixes

Author: pimterry

package-lock.json

@@ -67,7 +67,7 @@
     "mime-types": "^2.1.27",
     "mobx": "^6.3.5",
     "mockrtc": "^0.2.0",
-    "mockttp": "^3.3.0",
+    "mockttp": "^3.3.1",
     "node-abort-controller": "^3.0.1",
     "node-fetch": "^2.6.1",
     "node-forge": "^1.3.0",