Update key name in README

Author: jonasbb

README.md

@@ -56,7 +56,7 @@ Afterward, the `components` and `target` specified via inputs are installed in a
 | `cache`            | Automatically configure Rust cache (using [`Swatinem/rust-cache`])                     | true          |
 | `cache-workspaces` | Propagates the value to [`Swatinem/rust-cache`]                                        |               |
 | `cache-on-failure` | Propagates the value to [`Swatinem/rust-cache`]                                        | true          |
-| `key`              | Propagates the value to [`Swatinem/rust-cache`]                                        |               |
+| `cache-key`        | Propagates the value to [`Swatinem/rust-cache`] as `key`                               |               |
 | `matcher`          | Enable problem matcher to surface build messages and formatting issues                 | true          |
 | `rustflags`        | Set the value of `RUSTFLAGS` (set to empty string to avoid overwriting existing flags) | "-D warnings" |