Remove broken Amazon App Store production deploy

[jpelgrom]

Summary

The Amazon App Store submission in production releases is currently failing with

error

 [20:19:40***: The amazon_app_submission plugin is working!
[20:19:40***: Fetching app access token
[20:19:40***: Getting current edit
[20:19:41***: Get current apk id
[20:19:41***: Get current apk ETag
[20:19:42***: Replacing the apk with apk from 
+------------------------------------------+
|               Lane Context               |
+------------------+-----------------------+
| DEFAULT_PLATFORM | android               |
| PLATFORM_NAME    | android               |
| LANE_NAME        | android submit_amazon |
+------------------+-----------------------+
[20:19:42***: No such file or directory @ rb_sysopen - 

It appears that the current flow of prepare beta each week, release later doesn't work with the plugin* ugroupmedia/fastlane-plugin-amazon-app-store-submission#19 and fastlane/fastlane#15148 (comment) even suggests that submitting is never possible via the API.

To prevent failures, this PR removes the Amazon step from our production release flow and updates the README to provide more info on the release process.

 

* and the plugin is not really maintained looking at issues/open PRs

Screenshots

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Link to pull request in Documentation repository

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Any other notes