Documentation claims `toolchain: stable` is default, but it is not.

[jwalton]

Description

The README.md says that the "stable" toolchain is the default:

But if you don't specify a toolchain, you get:

Error: toolchain input was not given and repository does not have a rust-toolchain file

(See https://github.com/jwalton/rust-tokio-task-tracker/actions/runs/6436035135/job/17478566687).

Workflow code

name: Test

on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Install Rust
        uses: actions-rs/toolchain@v1
      - run: cargo test
      - run: cargo clippy

Action output

   with:
    default: false
    override: false
Error: toolchain input was not given and repository does not have a rust-toolchain file

Expected behavior

Should default to toolchain: default.