[trival] Fix typo introduced into rpc/protocol.h in commit 338bf06

The typo was introduced in commit 338bf065a4, which was merged yesterday.

Changes summarized to facilitate reviewing:
* exampled → example

src/rpc/protocol.h

@@ -39,7 +39,7 @@ enum RPCErrorCode
     RPC_METHOD_NOT_FOUND = -32601,
     RPC_INVALID_PARAMS   = -32602,
     // RPC_INTERNAL_ERROR should only be used for genuine errors in bitcoind
-    // (for exampled datadir corruption).
+    // (for example datadir corruption).
     RPC_INTERNAL_ERROR   = -32603,
     RPC_PARSE_ERROR      = -32700,