docs: remove "synchronous" from core description

Author: gadomski

README.md

@@ -20,7 +20,7 @@ This monorepo contains several crates:
 
 | Crate | Description | Badges |
 | ----- | ---- | --------- |
-| [stac](./core/README.md) | Core data structures and synchronous I/O | [![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/stac-utils/stac-rs/core.yml?style=flat-square)](https://github.com/stac-utils/stac-rs/actions/workflows/core.yml) <br /> [![docs.rs](https://img.shields.io/docsrs/stac?style=flat-square)](https://docs.rs/stac/latest/stac/) <br> [![Crates.io](https://img.shields.io/crates/v/stac?style=flat-square)](https://crates.io/crates/stac) |
+| [stac](./core/README.md) | Core data structures and I/O | [![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/stac-utils/stac-rs/core.yml?style=flat-square)](https://github.com/stac-utils/stac-rs/actions/workflows/core.yml) <br /> [![docs.rs](https://img.shields.io/docsrs/stac?style=flat-square)](https://docs.rs/stac/latest/stac/) <br> [![Crates.io](https://img.shields.io/crates/v/stac?style=flat-square)](https://crates.io/crates/stac) |
 | [stac-api](./api/README.md) | Data structures for the [STAC API](https://github.com/radiantearth/stac-api-spec) specification | [![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/stac-utils/stac-rs/api.yml?style=flat-square)](https://github.com/stac-utils/stac-rs/actions/workflows/api.yml) <br /> [![docs.rs](https://img.shields.io/docsrs/stac-api?style=flat-square)](https://docs.rs/stac-api/latest/stac_api/) <br> [![Crates.io](https://img.shields.io/crates/v/stac-api?style=flat-square)](https://crates.io/crates/stac-api) |
 | [stac-cli](./cli/README.md)| Command line interface | [![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/stac-utils/stac-rs/cli.yml?style=flat-square)](https://github.com/stac-utils/stac-rs/actions/workflows/cli.yml) <br /> [![docs.rs](https://img.shields.io/docsrs/stac-cli?style=flat-square)](https://docs.rs/stac-cli/latest/stac_cli/) <br> [![Crates.io](https://img.shields.io/crates/v/stac-cli?style=flat-square)](https://crates.io/crates/stac-cli) |
 | [stac-server](./server/README.md)| STAC API server with multiple backends | [![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/stac-utils/stac-rs/server.yml?style=flat-square)](https://github.com/stac-utils/stac-rs/actions/workflows/server.yml) <br /> [![docs.rs](https://img.shields.io/docsrs/stac-server?style=flat-square)](https://docs.rs/stac-server/latest/stac_server/) <br> [![Crates.io](https://img.shields.io/crates/v/stac-server?style=flat-square)](https://crates.io/crates/stac-server) |