Fix a typo

Summary: Minor styling fix.

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10478
Remove a useless function from `ArcanistMergeConflictLinter`

Summary: This function doesn't achieve anything.

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10477
Fix custom severity rules not being applied

Summary: It seems that `severity.rules` does not override the default linter severities set by the `ArcanistLinter` itself. This seems incorrect and counter-intuitive.

Test Plan: Created a `"severity.rules": { "(.*)": "disabled" }"` configuration and verified that it was being applied.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10475