RFR: 8269147: Update GStreamer to version 1.18.4

[Joeri Sykora]

On Thu, 24 Jun 2021 02:50:08 GMT, Alexander Matveev <almatvee at openjdk.org> wrote:

> - GStreamer updated to 1.18.4.
>  - Tested on all platforms with all formats.

We've also tested the changes on our build infrastructure and it all worked fine.

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Marked as reviewed by sykora (Author).

PR: https://git.openjdk.java.net/jfx/pull/541