chore: bump chromium to 129.0.6650.0 (main) (#43266)

* chore: bump chromium in DEPS to 129.0.6645.0

* chore: update patches

* chore: bump chromium in DEPS to 129.0.6646.0

* refactor: remove ppapi dependency

PPAPI removal - https://issues.chromium.org/issues/40511450
PDF viewer migration - https://issues.chromium.org/issues/40511452

* chore: update patches

* chore: enable `content_enable_legacy_ipc`

We were indirectly relying on this via `enable_ppapi=true`, with
633a57d9b6 ppapi is now disabled and
this commit makes the dependency explicit.

* fix: gn check

---------

Co-authored-by: electron-roller[bot] <84116207+electron-roller[bot]@users.noreply.github.com>
Co-authored-by: deepak1556 <hop2deep@gmail.com>

script/gn-check.js

@@ -29,7 +29,8 @@ env.PATH = `${env.PATH}${path.delimiter}${DEPOT_TOOLS}`;
 const gnCheckDirs = [
   '//electron:electron_lib',
   '//electron:electron_app',
-  '//electron/shell/common/api:mojo'
+  '//electron/shell/common:mojo',
+  '//electron/shell/common:plugin'
 ];
 
 for (const dir of gnCheckDirs) {