Clean up old USE_* and RELEASE.md notes.

RELEASE.md

@@ -2,12 +2,6 @@
 
 We have attempted to document known bugs and limitations - in particular the [HIP Kernel Language](docs/markdown/hip_kernel_language.md) document uses the phrase "Under Development", and the [HIP Runtime API bug list](http://gpuopen-professionalcompute-tools.github.io/HIP/bug.html) lists known bugs. 
 
-Upcoming:
-- Stability: Enforce periodic host synchronization to reclaim resources if the application has launched a large
-  number of commands (>1K) without synchronizing.  
-- Register keyword now silently ignored on HCC (previously would emit warning).
-- Doc updates: Add some more frequently asked questions to FAQ, fix TOC in some files, review.
-- Cookbook.
 
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