Fix the managed Bedrock logout test assertion (#33848)

## What changed

Update the expected `Account::AmazonBedrock` value to assert
`uses_codex_managed_credentials` when verifying the account before logout.

GitOrigin-RevId: 4d2dfa7b0422a420940ee20d44103cf3b2d483ad

codex-rs/app-server/tests/suite/v2/account.rs

@@ -1356,7 +1356,7 @@ async fn logout_managed_bedrock_restores_default_account() -> Result<()> {
         read_account(&mut mcp).await?,
         GetAccountResponse {
             account: Some(Account::AmazonBedrock {
-                credential_source: AmazonBedrockCredentialSource::CodexManaged,
+                uses_codex_managed_credentials: true,
             }),
             requires_openai_auth: false,
         }