Bump version to 3.2.0.rc.1

Merge pull request rubygems#3773 from rubygems/bundler3_binstub

Convert bundler2 binstub to bundler3

Bump version to 3.1.4

Bump version to 3.1.3

Bump version to 3.0.8

Allow failure with Ruby 2.3.8 because simple-cov-html does not suppor…

…t Ruby 2.3

Also bump up gemspec

Bump version to 3.1.1

History

Merge rubygems#2988

2988: Backport ruby core for Ruby 2.7 r=hsbt a=hsbt

# Description:

@mame and @ko1 fixed some issues for RubyGems 3.1.0.pre3 with Ruby 2.7.0-preview3. 

______________

# Tasks:

- [ ] Describe the problem / feature
- [ ] Write tests
- [ ] Write code to solve the problem
- [ ] Get code review from coworkers / friends

I will abide by the [code of conduct](https://github.com/rubygems/rubygems/blob/master/CODE_OF_CONDUCT.md).


Co-authored-by: Yusuke Endoh <[email protected]>
Co-authored-by: Koichi Sasada <[email protected]>
Co-authored-by: Hiroshi SHIBATA <[email protected]>