Structured data broken by `amphtml` link relation in AMP-to-AMP linking

[milindmore22]

Bug Description

In a recent support topic, we found out that BreadCrumbList schema (RDFa) doesn't allow rel="amphtml" attributes and marks structured data as invalid, As per discussion on slack Weston suggested we don't need it.

Example HTML Snippet :

<div class="breadcrumb" typeof="BreadcrumbList" vocab="https://schema.org/">
	<span property="itemListElement" typeof="ListItem">
	    <a property="item" typeof="WebPage" title="Go to Visitor Guard®." href="https://www.example.com?amp" class="home" rel="amphtml">
	        <span property="name">
	            Home
	        </span>
	   </a>
	<meta property="position" content="1">
	</span>
	<span class="post post-page current-item">
	    The Page Title
	 </span>
</div>

Tests :

1. Invalid Test
2. Valid Test

Expected Behaviour

The page links should be served without "rel="amphtml" attributes.

Steps to reproduce

1. Install and activate BreadCrumb Navxt Plugin
2. Add Breadcrumb to your site
3. Check the Structured Data on https://search.google.com/test/rich-results
4. See error

Additional context

• WordPress version: 5.8.1
• Plugin version: 2.1.4
• Gutenberg plugin version (if applicable):
• AMP plugin template mode: Transional Mode / Reader Mode
• PHP version: 7.4
• OS: Mac
• Browser: chrome, safari
• Device: Macbook Air

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Acceptance criteria

Implementation brief

QA testing instructions

Demo

Changelog entry

[westonruter]

I've made an inquiry as to whether rel should indeed be invalid here.

[westonruter]

OK, we should indeed omit the amphtml relation. We can discontinue adding relations altogether. They aren't being used anwayway, so they're just extra decoration.

[milindmore22]

QA Passed

Input

<a rel="noreferrer noopener" href="https://amp-local.test/hello-world/" data-type="post" data-id="1" target="_blank">Internal Link to AMP Page – Should not have amphtml</a>

Output

<a rel="noreferrer noopener" href="https://amp-local.test/hello-world/amp/" data-type="post" data-id="1" target="_blank">Internal Link to AMP Page – Should not have amphtml</a>

Input	amphtml	nonamphtml	Link Type
Internal Link to AMP page	Removed	N/A	Link to AMP page
Internal Link to non-AMP Page	Removed	N/A	Link to AMP Page ( redirects to non-AMP )
Internal Link with noamphtml attribute	Removed	Present	Link with nonamp=mobile parameter
External Link	Removed	N/A	No change
External Link with noamphtml attribute	Removed	Present	No change