Add 'Copy content from last week' text to prioritization procedure (#433)

Author: spastorino

src/compiler/prioritization/procedure.md

@@ -53,6 +53,7 @@ High level overview:
 - Notify WG leads about [next week's
   checkins](https://rust-lang.github.io/compiler-team/about/triage-meeting/)
 - Create an empty agenda using [our template](https://hackmd.io/WQW0yzDDS16YvtBNurmj6A), as soon as our Thursday's weekly meeting ends. After creating the meeting change document permissions to Write -> Owners.
+- Copy content from last week's agenda that is still pending. The relevant sections are `PRs waiting on team`, `P-critical`, `Unassigned P-high regressions` and `Nominated issues`.
 
 ### Prepare agenda content