Matrix with 3.0 value will install 3.1 ruby #252

I'm not totally sure that this is issue in ruby/setup-ruby iselft, but let me describe it

For quite a long time I've used this code block in different github actions in my different projects

name: Ruby
on: [push]
jobs:
  build:
    runs-on: ubuntu-latest
    continue-on-error: ${{ matrix.allow-failures }}
    strategy:
      matrix:
        ruby: [2.5, 2.6, 2.7, 3.0]
        allow-failures: [false]
        include:
          - ruby: head
            allow-failures: true
    steps:
    - uses: actions/checkout@v2
    ....all_other_steps

This worked well, it set up several ruby versions and run my tests

But with the release of ruby v3.1 I've noticed a very strange situation

That instead of v3.0 is v3.1 actually installed

You can take a look at that workflow
On Setup Ruby 3 stage in logs we see that:

Installing Bundler
  Using Bundler 2.3.2 from Gemfile.lock BUNDLED WITH 2.3.2
  /opt/hostedtoolcache/Ruby/3.1.0/x64/bin/gem install bundler -v 2.3.2
  Successfully installed bundler-2.3.2
  1 gem installed
  Took   0.57 seconds

First of all - I fought 'oh my bad, seems that if I send version as interger and not strings if will install latest major version

But I've rechecked version 2.6 - it send in config as 2.6, not a '2.6' and still installing it correctly, not latest v2.7

I see in docs - https://github.com/ruby/setup-ruby#matrix-of-ruby-versions that 3.0 is in quotes, but I don't quite get why only 3.0 need quotes?

And if quotes are really required - maybe add some readme statement about this to clarify reasons?