Bump webdev to f4856867de3e7b6ea6778dbc47cff44b12f9eed2

Changes:
```
> git log --format="%C(auto) %h %s" 718c39c..f485686
 https://dart.googlesource.com/webdev.git/+/f4856867 Use AOT snapshot of kernel_worker (2591)
 https://dart.googlesource.com/webdev.git/+/c0ac2196 Use 'compile js-dev' instead of invoking DDC directly (2579)
 https://dart.googlesource.com/webdev.git/+/ee65f5c1 Update minimum sdk version required to 3.7.0 (2590)

```

Diff: https://dart.googlesource.com/webdev.git/+/718c39c3b10f6e77f767d70d1f30f8a6c8262d6f..f4856867de3e7b6ea6778dbc47cff44b12f9eed2/
Change-Id: I680ff840165c3233b964ecdb71b544bf35ed1582
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/412780
Reviewed-by: Srujan Gaddam <srujzs@google.com>
Commit-Queue: Srujan Gaddam <srujzs@google.com>
Auto-Submit: Jessy Yameogo <yjessy@google.com>
diff --git a/DEPS b/DEPS
index 399e08e..5577139 100644
--- a/DEPS
+++ b/DEPS
@@ -147,7 +147,7 @@
   "tools_rev": "b51f39d01f5a4af33428a0189cd62595c01e23de",
   "vector_math_rev": "533c513771d35312dcd0f69e662d729979882df1",
   "web_rev": "c2d5f63e9ea4c1409d6e159fc7b92dbcf4dc0d4d",
-  "webdev_rev": "718c39c3b10f6e77f767d70d1f30f8a6c8262d6f", # b/398884799
+  "webdev_rev": "f4856867de3e7b6ea6778dbc47cff44b12f9eed2", # b/398884799
   "webdriver_rev": "b4fd8592fb9b1405fea3979cab88bcd857f2addb",
   "webkit_inspection_protocol_rev": "effa75205516757795683d527c3dea9546eb0c32",