Changed account editing section to use Stripe billing portal data attribute

[sam-lord]

closes GVA-649

We do still support the old edit-billing attribute, but this is the new way of accessing the full Stripe customer billing portal instead of the card update flow.

[coderabbitai]

Walkthrough

The documentation in the members theme file was updated to reflect managing billing and receipts via the Stripe customer portal. Wording changed from "Edit billing info" to "Manage billing & receipts". A data attribute was renamed from data-members-edit-billing to data-members-manage-billing. The previous data-members-success and data-members-cancel redirect attributes were removed and replaced with a single data-members-return attribute pointing to the return URL. A trailing newline was added after a code fence.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: updating the account editing section to use the Stripe billing portal data attribute, which directly matches the file modifications.
Description check	✅ Passed	The description is related to the changeset, explaining the motivation (transitioning to Stripe billing portal) and noting backward compatibility with the older edit-billing attribute.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@themes/members.mdx`:
- Around line 423-427: The anchor uses the old attribute name
data-members-edit-billing while the earlier example uses
data-members-manage-billing; update the anchor element to use the consistent
attribute data-members-manage-billing (replace data-members-edit-billing with
data-members-manage-billing) so both examples match and readers aren’t confused;
locate the anchor with the existing attributes data-members-return and the link
text "Manage billing & receipts" to apply the change.

[aileen]

👍