Remove duplicate definition added by https://github.com/brave/brave-core/pull/509

[darkdh]

fix brave/brave-browser#1309

Auditor: @yrliou, @bbondy, @mbacchi

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Needed or QA/No-QA-Needed) to include the closed issue in milestone

Test Plan:

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

[yrliou]

LGTM, confirmed it fix build errors on mac

[darkdh]

master: 7c61da4
0.55.x: f3f65bc
0.56.x: 374d83c