Add a trailing slash to iam/security-credentials/ when querying IMDS (#1487)

CHANGELOG.next.toml

aws/rust-runtime/aws-config/src/imds/credentials.rs

...default-provider-chain/imds_assume_role/http-traffic.json

...rovider-chain/imds_config_with_no_creds/http-traffic.json

...provider-chain/imds_default_chain_error/http-traffic.json

...ovider-chain/imds_default_chain_retries/http-traffic.json

...ovider-chain/imds_default_chain_success/http-traffic.json

...default-provider-chain/imds_no_iam_role/http-traffic.json