docs(colors): Remove references to WCAG AA

We only test against APCA in standard light/dark modes.

docs/product/base/color-fundamentals.html

@@ -370,7 +370,7 @@
 
     <section class="stacks-section">
         {% header "h2", "Accessibility standards" %}
-        <p class="stacks-copy">Stacks aims to equip you with an accessible color palette and has been tested against WCAG AA, WCAG AAA and the newer APCA color standards. Most of our color combinations meet WCAG AA and APCA levels defined below. We also offer high contrast mode which offers a greater level of contrast. </p>
+        <p class="stacks-copy">Stacks aims to equip you with an accessible color palette. The standard light and dark modes have been tested against <a class="s-link" href="https://git.myndex.com/">APCA</a> color standards, while high contrast modes have been tested against <a class="s-link" href="https://www.w3.org/WAI/WCAG2AAA-Conformance">WCAG AAA</a>. Most of our color combinations meet the APCA levels defined below. We also offer high contrast mode which offers a greater level of contrast.</p>
 
         {% for section in colors[0].accessibility %}
             <section class="stacks-section">