CDP: Deprecate AppCache domain

AppCache is being removed from Chromium
in crbug.com/1084190. This CL deprcates
AppCache debugging support in CDP with
the intention of removing it soon.

Bug: chromium:1084190
Change-Id: Ia40c7e529addff2e2a87c9cd30e745abb0f9c0d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3173217
Commit-Queue: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/main@{#924036}

third_party/blink/public/devtools_protocol/browser_protocol.pdl

@@ -408,7 +408,8 @@ experimental domain Animation
       # Animation that was started.
       Animation animation
 
-experimental domain ApplicationCache
+# The domain is deprecated as AppCache is being removed (see crbug.com/582750).
+experimental deprecated domain ApplicationCache
   depends on Page
 
   # Detailed application cache resource information.