style-checker correctly complains that PlatformMouseEvent.h is unnecessarily indented in the `WebCore` namespace. Let's fix this.
<rdar://problem/115590961>
Pull request: https://github.com/WebKit/WebKit/pull/17846
Committed 268070@main (d536c41672d0): <https://commits.webkit.org/268070@main> Reviewed commits have been landed. Closing PR #17846 and removing active labels.