refactor(): replace deprecated findProgramAddress with findProgramAdd…

…ressSync

The signature '(seeds: (Buffer | Uint8Array)[], programId: PublicKey): Promise<[PublicKey, number]>' of 'web3.PublicKey.findProgramAddress' is deprecated.

Updated the code to use the recommended 'findProgramAddressSync' method for better compatibility.

content/courses/native-onchain-development/deserialize-custom-data-frontend.md

@@ -97,7 +97,7 @@ account per note where each PDA is derived with the user’s public key and the
 note’s title.
 
 ```typescript
-const [pda, bump] = await web3.PublicKey.findProgramAddress(
+const [pda, bump] = await web3.PublicKey.findProgramAddressSync(
   [publicKey.toBuffer(), Buffer.from("Shopping list")],
   programId,
 );