updating_clang.md: Add dawn-win-x86-deps-rel tryjob

Bug: 1046362
Change-Id: Icdcc5226c4bb0ee6c8d58b33bb70f3494c55313e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2026967Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Auto-Submit: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736215}

docs/updating_clang.md

@@ -55,7 +55,8 @@ An archive of all packages built so far is at https://is.gd/chromeclang
       -b linux_chromium_chromeos_msan_rel_ng -b linux-chromeos-dbg \
       -b win-asan -b chromeos-amd64-generic-cfi-thin-lto-rel \
       -b linux_chromium_compile_dbg_32_ng -b win7-rel \
-      -b win-angle-deqp-rel-32 -b win-angle-deqp-rel-64 &&
+      -b win-angle-deqp-rel-32 -b win-angle-deqp-rel-64 \
+      -b dawn-win10-x86-deps-rel &&
     git cl try -B chrome/try -b iphone-device -b ipad-device \
       -b linux-chromeos-chrome
     ```