Force the react-native-video fork to build against same RN version as gutenberg-mobile from maven repo

[hypest]

This reverts commit 4085aeb.

Fixes #1761

It's not clear yet why the issue is happening but, reverting in order to patch and unblock the v1.20 editor release.

Edit: With 39f9f34, I'm pointing to a react-native-video version (here's the branch) that builds using a specific RN version (same as gutenberg-mobile at the moment of writing) and only fetching it from our remote RN maven mirror on Bintray.

To test:

1. On an Android 7 or 8 (possibly 9 too) device, run WPAndroid against this PR
2. Have a post with a vertical video in a vide block. Example content:

<!-- wp:paragraph -->
<p>hello world!</p>
<!-- /wp:paragraph -->
<!-- wp:video {"autoplay":false,"id":248,"loop":false,"muted":false,"playsInline":false,"src":"https://tuggytestgmb1.wpcomstaging.com/wp-content/uploads/2020/01/VID_20200109_173921.mp4"} -->
<figure class="wp-block-video"><video controls src="https://tuggytestgmb1.wpcomstaging.com/wp-content/uploads/2020/01/VID_20200109_173921.mp4"></video></figure>
<!-- /wp:video -->

3. Open the post
4. Tap on the video block and then its caption
5. the video preview should be visible and no overflow should be happening

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[Tug]

Can confirm, this revert fixes it for me 👍

[Tug]

Still works with the last commit!

[mchowning]

This is fixing the video issue for me as well.