Fix x-wallet-address header in README.md (#142)

Author: adam-maj

README.md

@@ -75,7 +75,7 @@ docker run -e .env -p 3005:3005 thirdweb/engine:latest
 - In development mode, go to the server url to see an admin interface
 - Every request to the server requires an authentication token for admin actions use the thirdweb SecretKey. Use the `Authorization` Header to set the value shown below:
   - `Authorization: Bearer: <thirdweb SecretKey>`
-- Every write request to the server also requires the `X-Wallet-Address` header to specify which admin wallet to send a transaction with. Use the following format to set this header:
+- Every write request to the server also requires the `x-wallet-address` header to specify which admin wallet to send a transaction with. Use the following format to set this header:
 
   - `X-Wallet-Address: 0x3ecdbf3b911d0e9052b64850693888b008e18373`