tests/sigchild.sh: try to fix intermittent fail (re: dc80f40d)

It probably won't make a difference since the 'sleep' is run in the
background, but let's change 'sleep .5 &' back to the original
'sleep 1 &' from the 93u+ 2012-08-01 version and see what happens.

See: https://github.com/ksh93/ksh/issues/344#issuecomment-982219206

src/cmd/ksh93/tests/sigchld.sh

@@ -68,7 +68,7 @@ then
 		integer running=0 maxrunning=0
 		trap "((running--))" CHLD
 		for ((i=0; i<JOBCOUNT; i++))
-		do	sleep .5 &
+		do	sleep 1 &
 			if	((++running > maxrunning))
 			then	((maxrunning=running))
 			fi