Change all `MiniTest` to `Minitest` since, `MiniTest` namespace has been renamed to `Minitest`
Ref: https://github.com/seattlerb/minitest/blob/master/History.txt
Fix to_param when attribute has multibyte character
Merge pull request #13386 from rono23/fix-to-param

Fix to_param when attribute has multibyte character
Unused classes in test case
Merge pull request #13366 from vipulnsward/minitest-namespace-change

Change all `MiniTest` to `Minitest`