Update WebView change ID releases.

The ENABLE_FILE_SYSTEM_ACCESS and ENABLE_USER_AGENT_REDUCTION compat
changes did not ship in B as originally planned (the flags guarding the
features were not enabled). Update the annotations on the compat change
IDs to indicate that they will be enabled for apps targeting C instead
in preparation for rolling these out again.

The compat changes will still not actually be enabled until the flags
are turned on.

Bug: 371034303
Bug: 40101963
Test: n/a
Flag: android.webkit.file_system_access
Flag: android.webkit.user_agent_reduction
Change-Id: I52aa4addc7314fd21e8ab96025833ffe856ebd26