docs: fix markdown syntax in debugging-with-swarming

Leading "- " sets off a list in markdown, oops :)

TBR=agable@chromium.org

Bug: None
Change-Id: I12bf7bcd460a9751c92c2c1e0aa3c5328e5d0382
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1790377Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694916}

docs/workflow/debugging-with-swarming.md

@@ -93,8 +93,8 @@ The `isolate.py` tool will emit something like this:
 e625130b712096e3908266252c8cd779d7f442f1  unit_tests
 ```
 
-Do not ctrl-c it after it does this, even if it seems to be hanging for a minute
-- just let it finish.
+Do not ctrl-c it after it does this, even if it seems to be hanging for a
+minute - just let it finish.
 
 ## Running an isolate