NEWS: improve bullet about MPI_THREAD_MULTIPLE

Signed-off-by: Jeff Squyres <[email protected]>

(cherry picked from commit open-mpi/ompi@8e01674)

Author: jsquyres

NEWS

@@ -78,7 +78,8 @@ included in the vX.Y.Z section and be denoted as:
   Version 1.1.2 of PMIx is included internally in this release.
 - Add support for PLFS file systems in Open MPI I/O.
 - Add support for UCX transport.
-- Improved support for MPI_THREAD_MULTIPLE.
+- Improved support for MPI_THREAD_MULTIPLE (when configured with
+  --enable-mpi-thread-multiple).
 - Simplify build process for Cray XC systems.  Add support for
   using native SLURM.
 - Updated internal/embedded copies of third-part software: