lib: use bracket notation instead of startsWith/endsWith for single char

Author: kimtaejin3

lib/internal/socketaddress.js

@@ -157,7 +157,7 @@ class SocketAddress {
         hostname: address,
         port,
       } = URLParse(`http://${input}`);
-      if (address.startsWith('[') && address.endsWith(']')) {
+      if (address[0] === '[' && address[address.length - 1] === ']') {
         return new SocketAddress({
           address: address.slice(1, -1),
           port: port | 0,