Add missing spaces in CSS calc function

[DanielRuf]

Description (*)

This PR adds the missing spaces in the CSS calc() function as this won't work in all browsers without it.

Fixed Issues (if relevant)

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

Manual testing scenarios (*)

1. ...
2. ...

Questions or comments

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 are green)

[m2-assistant]

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[magento-engcom-team]

Hi @kalpmehta, thank you for the review.
ENGCOM-6135 has been created to process this Pull Request
✳️ @kalpmehta, could you please add one of the following labels to the Pull Request?

Label	Description
Auto-Tests: Covered	All changes in Pull Request is covered by auto-tests
Auto-Tests: Not Covered	Changes in Pull Request requires coverage by auto-tests
Auto-Tests: Not Required	Changes in Pull Request does not require coverage by auto-tests

[engcom-Alfa]

QA not applicable

[m2-assistant]

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