Roll Fuchsia SDK from 29.20250731.5.1 to 29.20250804.4.1

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/fuchsia-sdk-dart-sdk
Please CC [email protected] on the revert to ensure that a human
is aware of the problem.

To file a bug in Fuchsia SDK: https://bugs.fuchsia.dev/p/fuchsia/issues/list
To file a bug in Dart SDK: https://github.com/dart-lang/sdk/issues

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

Cq-Include-Trybots: luci.dart.try:vm-fuchsia-release-x64-try;luci.dart.try:vm-fuchsia-release-arm64-try
Change-Id: I752348f3512545b8675f61593b5d15109cb09dcb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/443640
Reviewed-by: Alexander Markov <[email protected]>
Commit-Queue: Alexander Markov <[email protected]>
Reviewed-by: Alexander Aprelev <[email protected]>

Author: DEPS Autoroller

DEPS

@@ -84,7 +84,7 @@ vars = {
   "download_reclient": True,
 
   # Update from https://chrome-infra-packages.appspot.com/p/fuchsia/sdk/core
-  "fuchsia_sdk_version": "version:29.20250731.5.1",
+  "fuchsia_sdk_version": "version:29.20250804.4.1",
   "download_fuchsia_deps": False,
 
   # Ninja, runs the build based on files generated by GN.