[landing] Remove redundant `margin-left` and `margin-right`
[landing] Remove redundant `margin-left` and `margin-right`

Summary: addressed feedback from D1548

Test Plan: continues to look as expected

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: KatPo, palys-swm, Adrian

Differential Revision: https://phabricator.ashoat.com/D1555

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