[fuchsia] Update the "deprecated-shell" feature to "hub"

The "hub" feature is the permanent replacement for the
"deprecated-shell" feature.

Bug: 977730
Change-Id: I3212a39f8d8acce39a33470d63a5dc1d8aa4d965
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1848651
Auto-Submit: Fabrice de Gans-Riberi <fdegans@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705281}

fuchsia/engine/web_engine_integration_tests.cmx

 {
   "sandbox": {
     "features": [
-      "deprecated-shell",
       "deprecated-ambient-replace-as-executable",
+      "hub",
       "isolated-persistent-storage",
       "isolated-temp"
     ],