Remove custom shipping_phone handling (requires WC 5.6+)

[github-actions]

Remove custom shipping_phone handling (requires WC 5.6+)

set_shipping_phone was added in 5.6 https://woocommerce.github.io/code-reference/classes/WC-Order.html#method_set_shipping_phone
This comment was added before 5.6 got released.
Now we're on 6.8 we can remove the code that handles pre-5.6 WC

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https://github.com/woocommerce/woocommerce-gutenberg-products-block/blob/2bfe6deda4ef3f94972466290b3d7484e13c3182/src/StoreApi/Routes/CartUpdateCustomer.php#L123-L132

🚀 This issue was generated by the automations bot based on a todo comment in 2bfe6de when #4268 was merged. cc @mikejolley

[github-actions]

This issue has been marked as stale because it has not seen any activity within the past 60 days. Our team uses this tool to help surface issues for review. If you are the author of the issue there's no need to comment as it will be looked at.

Internal: After 10 days with no activity this issue will be automatically be closed.

[github-actions]

This issue has been marked as stale because it has not seen any activity within the past 60 days. Our team uses this tool to help surface issues for review. If you are the author of the issue there's no need to comment as it will be looked at.

Internal: After 10 days with no activity this issue will be automatically be closed.

[github-actions]

This issue has been marked as stale because it has not seen any activity within the past 60 days. Our team uses this tool to help surface issues for review. If you are the author of the issue there's no need to comment as it will be looked at.

Internal: After 10 days with no activity this issue will be automatically be closed.

[Aljullu]

@ralucaStan maybe this one needs to be re-opened?

[ralucaStan]

Thank you @Aljullu, I've reopened it.

[masteradhoc]

@ralucaStan is it possible this was already fixed by #5326 ?

[ralucaStan]

Nice catch @masteradhoc! ✋
Closing the ticket, the legacy set_shipping_phone was removed in #5326