Update README.md

Fixed a supposed typo where instead of client, terra should've been used. The previous code would not run.

README.md

@@ -59,14 +59,14 @@ Terra.js can be used in Node.js, as well as inside the browser. Please check the
 import { LCDClient, Coin } from '@terra-money/terra.js';
 
 // connect to pisco testnet
-const client = new LCDClient({
+const terra = new LCDClient({
   URL: 'https://pisco-lcd.terra.dev',
   chainID: 'pisco-1',
   isClassic: false  // if it is unset, LCDClient assumes the flag is false.
 });
 
 // connect to columbus-5 terra classic network
-const client = new LCDClient({
+const terra = new LCDClient({
   URL: 'https://columbus-lcd.terra.dev',
   chainID: 'columbus-5',
   isClassic: true  // *set to true to connect terra-classic chain*