LICENSE.iceberg does not list the bundled google-auth libraries

### Describe the bug

Since `531058d2e`, `iceberg/iceberg-common` declares `implementation(libs.google.auth.http)`. That puts `google-auth-library-oauth2-http` — and its transitive `google-auth-library-credentials`, which the POM declares at compile scope — into the `gravitino-iceberg-rest-server` distribution. `LICENSE.iceberg` has no entry for either.

`LICENSE.bin` already lists both under the BSD section, so the fix is to bring `LICENSE.iceberg` in line.

No `NOTICE` change is required: `NOTICE.bin` carries no google-auth entry.

### Affects

`main` (2.0.0) and `branch-1.3` (1.3.1). Found during the 1.3.1 LICENSE/NOTICE audit.

Compare LICENSE.iceberg with the existing google-auth entries in LICENSE.bin, focusing on google-auth-library-oauth2-http and google-auth-library-credentials. Add both missing libraries under the BSD section, leave NOTICE unchanged as requested, and verify the entries match the bundled distribution and apply to the affected branches.

Written by the indexing model from the issue text.