Update the CDN (#1720)

No linked issue

### This PR:
<!-- Describe what this PR adds to this repo and why -->
<!-- E.g. -->
<!-- * Implements feature 1 -->
<!-- * Fixes bug 3 -->

Resolves a potential issue with the CDN during restart tests. Aborts
futures related to the main `start()` future if that one gets killed or
is aborted.

CDN related changes here:
https://github.com/EspressoSystems/Push-CDN/pull/50/files

 cc @jbearer

Cargo.toml

@@ -68,11 +68,11 @@ hotshot-example-types = { git = "https://github.com/EspressoSystems/hotshot", ta
 cdn-broker = { git = "https://github.com/EspressoSystems/Push-CDN", features = [
   "runtime-async-std",
   "global-permits",
-], tag = "0.4.2", package = "cdn-broker" }
+], tag = "0.4.3", package = "cdn-broker" }
 cdn-marshal = { git = "https://github.com/EspressoSystems/Push-CDN", features = [
   "runtime-async-std",
   "global-permits",
-], tag = "0.4.2", package = "cdn-marshal" }
+], tag = "0.4.3", package = "cdn-marshal" }
 
 jf-plonk = { git = "https://github.com/EspressoSystems/jellyfish", tag = "0.4.5", features = [
   "test-apis",