test: use strictEqual in cwd-enoent

Changed all references from assert.Equal() to assert.strictEqual().

PR-URL: https://github.com/nodejs/node/pull/10077
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

test/parallel/test-cwd-enoent.js

@@ -21,6 +21,6 @@ proc.stdout.pipe(process.stdout);
 proc.stderr.pipe(process.stderr);
 
 proc.once('exit', common.mustCall(function(exitCode, signalCode) {
-  assert.equal(exitCode, 0);
+  assert.strictEqual(exitCode, 0);
-  assert.equal(signalCode, null);
+  assert.strictEqual(signalCode, null);
 }));