Update intro-to-cryptography.md

This error is shwoing when using 
```
import "dotenv/config"
```
Error [ERR_MODULE_NOT_FOUND]: Cannot find module 'D:\Coding\Solana\solKeyPair\node_modules\.bin\node_modules\dotenv\config.js' imported from D:\Coding\Solana\solKeyPair\node_modules\.bin\esrun-1723634828132.tmp.mjs
Did you mean to import ../../dotenv/config.js?

IF you use this then this error will be gonr

content/courses/intro-to-solana/intro-to-cryptography.md

@@ -218,7 +218,8 @@ SECRET_KEY="[(a series of numbers)]"
 We can then load the keypair from the environment. Update `generate-keypair.ts`:
 
 ```typescript
-import "dotenv/config";
+import dotenv from "dotenv";
+dotenv.config();
 import { getKeypairFromEnvironment } from "@solana-developers/helpers";
 
 const keypair = getKeypairFromEnvironment("SECRET_KEY");