tools: remove -raw-cmd usage for swarming

The flag is nop now.

Bug: 1142713
Change-Id: Iff9287d2d317fce85c06ba43cfaabf2fc66efbd3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2643000
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846180}

tools/infra/clobber_cache_utils.py

@@ -35,7 +35,6 @@ def _trigger_clobber(swarming_server, pool, cache, bot, mount_rel_path,
   cmd = [
       _SWARMING_CLIENT,
       'trigger',
-      '-raw-cmd',
       '-S',
       swarming_server,
       '-dimension',