Drop FixedVector::data() in favor of span() / mutableSpan().
Pull request: https://github.com/WebKit/WebKit/pull/29109
Committed 279328@main (a3a31351878e): <https://commits.webkit.org/279328@main> Reviewed commits have been landed. Closing PR #29109 and removing active labels.
<rdar://problem/128748242>