tests: Merge stderr and stdout in 0002-printf.sh

It simplifies the test shell script.

tests/0002-printf.sh

@@ -2,10 +2,9 @@
 
 set -e
 
-res1=tmp1.$$
-res2=tmp2.$$
+tmp=tmp.$$
 
-trap 'rm -f $res1 $res2' EXIT
+trap 'rm -f $tmp' EXIT
 trap 'exit $?' HUP INT TERM
 
 (
@@ -17,17 +16,14 @@ trap 'exit $?' HUP INT TERM
 	$EXEC ../printf '%+04d %+4d ' 1 2 3 -400; ../printf "\n"
 	# Missing format specifier; should have sane error message
 	$EXEC ../printf '%000' FOO || echo "Expected failure"
-) > $res1 2> $res2
+) > $tmp 2>&1
 
-diff -u - $res1 <<'EOF'
+diff -u - $tmp <<'EOF'
 123
 0
 foo
 bar
 +001   +2 +003 -400 
+../printf: Missing format specifier.
 Expected failure
 EOF
-  
-diff -u - $res2 <<'EOF'
-../printf: Missing format specifier.
-EOF