Copy text from constructor parameter to corresponding property (dotnet#10650)

I was having trouble figuring out if higher or lower values are "higher" priority. Some classic data structures use lower values for "higher" priorities, for instance.

This PR copies the text from the constructor's `priority` parameter, which does detail this, over to the corresponding `Priority` property.

Author: rickbrew

xml/System.Runtime.CompilerServices/OverloadResolutionPriorityAttribute.xml

@@ -61,7 +61,7 @@
         <ReturnType>System.Int32</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>The priority of the member.</summary>
+        <summary>The priority of the member. Higher numbers are prioritized, lower numbers are deprioritized.</summary>
         <value>To be added.</value>
         <remarks>To be added.</remarks>
       </Docs>