fix typo: change 'a Op-besu' to 'an Op-Besu' in node start section

Author: ozzy35410

docs/op-besu-docs/run-a-node/use_docker.md

@@ -29,7 +29,7 @@ openssl rand -hex 32 > jwt.txt
 mkdir datadir 
 ```
 
-## Start a Op-besu node
+## Start an Op-besu node
 
 <Tabs>
   <TabItem value="op sepolia" label="op sepolia" default>
@@ -83,4 +83,4 @@ The following settings are a security risk in production environments:
 - Setting `--host-allowlist` to `"*"` allows JSON-RPC API access from any host.
 - Setting `--rpc-http-cors-origins` to `"all"` or `"*"` allows cross-origin resource sharing (CORS) access from any domain.
 
-:::
+:::