Move normative text outside of informative notes

Author: svgeesus

compositing-1/Overview.bs

@@ -141,7 +141,7 @@ The syntax of the property of <<blend-mode>> is given with:
     <a value>hue</a> | <a value>saturation</a> | <a value>color</a> | <a value>luminosity</a>
 </pre>
 
-Note: Applying a blendmode other than <a value>normal</a> to the element must establish a new <a href="https://www.w3.org/tr/css21/visuren.html#x43">stacking context</a> [[!CSS21]]. This group must then be blended and composited with the <a href="https://www.w3.org/tr/css21/visuren.html#x43">stacking context</a> that contains the element.
+Applying a blendmode other than <a value>normal</a> to the element must establish a new <a href="https://www.w3.org/tr/css21/visuren.html#x43">stacking context</a> [[!CSS21]]. This group must then be blended and composited with the <a href="https://www.w3.org/tr/css21/visuren.html#x43">stacking context</a> that contains the element.
 
 <wpt>
   Blending_in_a_group_with_filter.html
@@ -826,7 +826,7 @@ if present.
 <h3 id="rootgroup">The Root Group</h3>
 The root group encompasses the entire canvas and contains (or is below) the root element group of the root element of a web page.
 
-<p class="note">Browsers often use an infinite <a href="https://www.w3.org/TR/css-color-4/#sample">white, 100% opaque</a> root group,
+<p class="note allow-2119">Browsers often use an infinite <a href="https://www.w3.org/TR/css-color-4/#sample">white, 100% opaque</a> root group,
 for final compositing, but this is not required.
 
 <h2 id="advancedcompositing">Advanced compositing features</h2>
@@ -1283,7 +1283,7 @@ The <a>backdrop</a> is replaced with the source where the source is lighter; oth
     B(Cb, Cs) = max(Cb, Cs)
 </pre>
 
-Note: The result must be rounded down if it exceeds the range.
+The result must be rounded down if it exceeds the range.
 
 <div class="figure">
 <img src="examples/lighten.png" alt="example of lighten blending">
@@ -1513,7 +1513,7 @@ Privacy Considerations</h2>
 
   <p>No new privacy considerations have been reported on this specification.</p>
 
-<h3 id="security" class="no-num">
+<h2 id="security" class="no-num">
 Security Considerations</h2>
 
 It is important that the timing to the blending and compositing operations is independent of the source and destination pixel. Operations must be implemented in such a way that they always take the same amount of time regardless of the pixel values.</p>