Remove spurious Makefile.am line

Author: Ralph Castain

opal/mca/pmix/pmix3x/pmix/src/Makefile.am

@@ -82,4 +82,3 @@ endif
 MAINTAINERCLEANFILES = Makefile.in config.h config.h.in
 DISTCLEANFILES = Makefile
 CLEANFILES = core.* *~
-AM_CFLAGS = -Wall