Fix DSQL SDK token generation example (#3937)

## Motivation and Context
This example doesn't reflect the token generation API accurately, this
PR fixes that.

## Description
Fix the example by using the right API.

## Testing
Documentation update on an ignored code block, no testing required

## Checklist
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aws/rust-runtime/aws-inlineable/src/dsql_auth_token.rs

@@ -36,7 +36,7 @@ const SERVICE: &str = "dsql";
 ///            .build()
 ///            .expect("cfg is valid"),
 ///    );
-///    let token = generator.auth_token(&cfg).await.unwrap();
+///    let token = generator.db_connect_admin_auth_token(&cfg).await.unwrap();
 ///    println!("{token}");
 /// }
 /// ```