[0029] Mark cooperative vectors proposal as rejected (microsoft#637)

The functionality provided by this proposal is now being exposed through
[0035-linalg-matrix.md](0035-linalg-matrix.md).

See
https://devblogs.microsoft.com/directx/shader-model-6-9-and-the-future-of-cooperative-vector/
for more context.

Author: damyanp

proposals/0029-cooperative-vector.md

@@ -8,9 +8,10 @@ params:
   sponsors:
   - damyanp: Damyan Pepper
   - pow2clk: Greg Roth
-  status: Under Review
+  status: Rejected
 ---
 
+> This has been superceded by [0035-linalg-matrix.md](0035-linalg-matrix.md)
 
 
 * Planned Version: SM 6.9