[Backport] Use proper variables for tooltip styles on tablet devices

[ansari-ziyaurrahman]

Original Pull Request
#22258

Description
There are variables available for tooltip customization. This commit fixes an issue
on tablet devices when trying to use them.

Fixed Issues (if relevant)

1. magento/magento2#<issue_number>: Issue title
2. ...

Manual testing scenarios (*)

1. Open Magento/blank/Magento_Checkout/web/css/source/module/checkout/_tooltip.less file and change the values of the tooltip variables as follows (Usually we do this via theme, but it's for testing purpose only):
   @checkout-tooltip-content__background-color: #fff; @checkout-tooltip-content__border-color: #f2f5f7; @checkout-tooltip-content__active__border-color: @checkout-tooltip-content__border-color;

2. Navigate to checkout and chec the new styles of field tooltips

3. Set the width to 768px and check them again:

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)

[m2-assistant]

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[orlangur]

@ansari-krish original commit author must be preserved

[orlangur]

@ansari-krish what do you want from me? Problem with commit authorship is still not fixed.

[sidolov]

@ansari-krish , I am closing this PR now due to inactivity.
Please, preserve the author of original PR and force push the branch if you wish to continue.
Thank you for the collaboration!

[m2-assistant]

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