Fix spelling mistake that has been there for a long, long time...

This commit was SVN r28562.

contrib/dist/linux/openmpi.spec

@@ -194,7 +194,7 @@
 #
 #############################################################################
 
-Summary: A powerful implementaion of MPI
+Summary: A powerful implementation of MPI
 Name: %{?_name:%{_name}}%{!?_name:openmpi}
 Version: $VERSION
 Release: 1