RFR: 8255378: [Vector API] Remove redundant vector length check after JDK-8254814 and JDK-8255210

[Jie Fu]

On Wed, 28 Oct 2020 10:07:50 GMT, Andrew Dinn <adinn at openjdk.org> wrote:

> This is arguably trivial and needs no review but here is one anyway.

Thanks @adinn for your review.
Pushed.

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PR: https://git.openjdk.java.net/jdk/pull/854