Removed unused _initDiscount() function

[mageprince]

Description

Remove unused commented function from tax.php

Fixed Issues

N/A

Manual testing scenarios

N/A

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-engcom-team]

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[VladimirZaets]

Hi @mageprince. Thanks for the collaboration. Due to Magento backward-compatible guide we can't remove the protected method usage. Someone can override this method in the self implementation.

[mageprince]

@VladimirZaets Yes you are right. We should not remove function due to Backward compatible development. But should remove the unused commented code from files.
There are some issue with this PR in my local so I created a new PR #16875