Update Mockttp for TLS fingerprint/unblocking improvements

This makes our TLS fingerprint very very nearly match Firefox,
sufficient to avoid many blocks, and also tweaks headers (dropping
proxy-connection headers in forwarding) to more closely match normal
client behaviour.

With this, we immediately stop seeing many server blocks, and the
remaining super strict blocks can generally be avoided by enabling
HTTP/2 as well.

Author: pimterry

package-lock.json

@@ -67,7 +67,7 @@
     "mime-types": "^2.1.27",
     "mobx": "^6.3.5",
     "mockrtc": "^0.2.0",
-    "mockttp": "^3.2.3",
+    "mockttp": "^3.3.0",
     "node-abort-controller": "^3.0.1",
     "node-fetch": "^2.6.1",
     "node-forge": "^1.3.0",