[css-highlight-api] Remove text for resolved highlight priority issues.

Author: sanketj

css-highlight-api-1/Overview.bs

@@ -356,27 +356,6 @@ Priority of Overlapping Highlights</h4>
 	When two ore more [=custom highlights=] have the same numerical priority,
 	the one most recently [=registered=] has the higher effective [=priority=].
 
-	Issue(4593): should negative numbers mean stacking
-	below the built-in [=highlight pseudo-elements=]?
-
-	Issue(4592): Should priority be an (unsigned) integer instead?
-	That would make comparisons more reliable,
-	but would likely lead to numbering reminiscent of BASIC line numbers.
-
-	Issue(4591): Should we drop priority by numbers entirely,
-	and replace it with some other ordering mechanism?
-	Experience with BASIC line number or z-index
-	does not give much confidence that ordering by number is a good idea.
-	Is placing in an ordered data-structure better?
-	Should authors be able to express a desired to be placed above/below
-	other named highlights,
-	and let the UA figure it out?
-
-	Issue(4594): Should the built-in [=highlight pseudo-elements=]
-	be exposed as well,
-	so that they too can be reordered,
-	and so that they can be interleaved with custom ones freely?
-
 	<div class=example id=overlap-highlight-ex>
 		<xmp highlight=html>
 			<style>