Remove redundant swarming default_priority assignment
Remove redundant swarming default_priority assignment

It is expected to be set by configure_swarming,
and changing it later causes "ng" trybots
to use lower priority.

BUG=380709

Review URL: https://codereview.chromium.org/736713002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@292999 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build