fixup! ci: track busybox-w32 main for the ash.exe artifact

BusyBox PR #17 gained two fixes required by Git's full test suite: the
NOFORK head now isolates stdin buffering, and `ash` closes redirected
script descriptors when restoring redirections.

Replace run 29563456146 with PR run 29837676933 so that every matrix leg
uses an identical corrected binary:

https://github.com/git-for-windows/busybox-w32/actions/runs/29837676933

The source SHA is 859d020281170e2e33eaabfbde30342b39afe6ee. Both push and
PR workflows passed, including the full BusyBox test suite. The artifact
is 844,288 bytes and has this SHA-256:

EC7DDA11CBB881526B79C19474A106490A88EA57DCB919832CE8522A0EBE67FA

Assisted-by: GPT-5.6 Sol
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

.github/workflows/main.yml

@@ -158,7 +158,7 @@ jobs:
         GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       run: |
         # TEMPORARY: use the artifact built for busybox-w32 PR #17.
-        gh run download -R git-for-windows/busybox-w32 29563456146 \
+        gh run download -R git-for-windows/busybox-w32 29837676933 \
           -n busybox -D bb &&
         test -f bb/busybox.exe &&
         cp bb/busybox.exe /mingw64/bin/ash.exe &&