[Issue] Shipping Estimation: Prevent Quote Double Saving

[m2-assistant]

This issue is automatically created based on existing pull request: #35631: Shipping Estimation: Prevent Quote Double Saving

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Description (*)

• Removes a seemingly superfluous additional saving of the quote when estimating shipping
  • The Magento\Checkout\Model\Cart::save() function also saves the quote in the same manner
• Only sets collectShippingRates once
  • The Magento\Checkout\Model\Cart::save() function also sets this

Manual testing scenarios (*)

1. Install sample data
2. Add a product to the cart
3. Proceed to the cart page
4. Estimate shipping using valid address data
5. Ensure the available shipping methods are displayed
6. Ensure the selecting of a shipping method updates cart totals correctly

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)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)

[github-jira-sync-bot]

✅ Jira issue https://jira.corp.adobe.com/browse/AC-7503 is successfully created for this GitHub issue.

[m2-assistant]

✅ Confirmed by @engcom-Echo. Thank you for verifying the issue.
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