test: Remove references to customFds

Option has been deprecated since v0.5.11

Signed-off-by: Fedor Indutny <fedor@indutny.com>

test/simple/test-child-process-set-blocking.js

@@ -27,7 +27,7 @@ var SIZE = 100000;
 var childGone = false;
 
 var cp = ch.spawn('python', ['-c', 'print ' + SIZE + ' * "C"'], {
-  customFds: [0, 1, 2]
+  stdio: 'inherit'
 });
 
 cp.on('exit', function(code) {

test/simple/test-regress-GH-1726.js

@@ -38,7 +38,7 @@ if (gen === maxGen) {
 }
 
 var child = ch.spawn(process.execPath, [__filename, gen + 1], {
-  customFds: [0, -1, 2]
+  stdio: 'inherit'
 });
 assert.ok(!child.stdin);
 assert.ok(child.stdout);