test: refactor test-child-process-stdio-inherit

assert.equal() -> assert.strictEqual()

PR-URL: nodejs#9893
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-child-process-stdio-inherit.js

@@ -22,10 +22,10 @@ function grandparent() {
   child.stdin.end(input);
 
   child.on('close', function(code, signal) {
-    assert.equal(code, 0);
-    assert.equal(signal, null);
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
     // cat on windows adds a \r\n at the end.
-    assert.equal(output.trim(), input.trim());
+    assert.strictEqual(output.trim(), input.trim());
   });
 }