test: use print() function in both Python 2 and 3

PR-URL: #29298
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rich Trott <rtrott@gmail.com>

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

@@ -26,7 +26,7 @@ const ch = require('child_process');
 
 const SIZE = 100000;
 
-const cp = ch.spawn('python', ['-c', `print ${SIZE} * "C"`], {
+const cp = ch.spawn('python', ['-c', `print(${SIZE} * "C")`], {
   stdio: 'inherit'
 });