Update Webdev pin

Pins DWDS to dart-lang/webdev@3078f48 which is necessary to unblock Dart SDK rollsdue to this change to the VM service interface: https://dart-review.googlesource.com/c/sdk/+/321660

Excludes dart-lang/webdev@d2dae56 which is a breaking change to DWDS.

Bug: dart-lang/webdev#2236
Change-Id: I3be3450901023dc5078f3aee1339ecf175908577
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/327022
Reviewed-by: Ben Konyi <[email protected]>
Commit-Queue: Ben Konyi <[email protected]>

Author: elliette

DEPS

@@ -189,7 +189,7 @@ vars = {
   "vector_math_rev": "d54af8a2b8b8d935a475a4da6ea5a1b343f29562",
   "watcher_rev": "1aed03e2a8005f45083fdb38cbd4b684cd23082f",
   "web_socket_channel_rev": "af945f1ad3ac4193ed70b4ebfbdcba3b9f0198bc",
-  "webdev_rev": "d7e0d1ff57d954ce4bb9e2201c87de092695701b",
+  "webdev_rev": "3078f48fb56a1036bc0f2a08ac51567291d8a837", # https://github.com/dart-lang/webdev/issues/2236
   "webdriver_rev": "21976d657e6505ad113f714bd104420aee23faac",
   "webkit_inspection_protocol_rev": "82f0c1c46dfdba5edf7c5fa84456233121dd69e1",
   "yaml_rev": "ae001879aa377afee2e70cf11b8716d6cc3e2658",