Replace outdated help.github.com URLs with docs.github.com

Author: fkmy

README.md

@@ -133,8 +133,8 @@ jobs:
 ```
 
 See the GitHub Actions documentation for more details about the
-[workflow syntax](https://help.github.com/en/actions/reference/workflow-syntax-for-github-actions)
-and the [condition and expression syntax](https://help.github.com/en/actions/reference/context-and-expression-syntax-for-github-actions).
+[workflow syntax](https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions)
+and the [condition and expression syntax](https://docs.github.com/en/actions/reference/context-and-expression-syntax-for-github-actions).
 
 ### Supported Version Syntax
 
@@ -252,7 +252,7 @@ Note that running CI on Windows can be quite challenging if you are not very fam
 It is recommended to first get your build working on Ubuntu and macOS before trying Windows.
 
 * Use Bundler 2.2.18+ on Windows (older versions have [bugs](https://github.com/ruby/setup-ruby/issues/209#issuecomment-889064123)) by not setting the `bundler:` input and ensuring there is no `BUNDLED WITH 1.x.y` in a checked-in `Gemfile.lock`.
-* The default shell on Windows is not Bash but [PowerShell](https://help.github.com/en/actions/automating-your-workflow-with-github-actions/workflow-syntax-for-github-actions#using-a-specific-shell).
+* The default shell on Windows is not Bash but [PowerShell](https://docs.github.com/en/actions/automating-your-workflow-with-github-actions/workflow-syntax-for-github-actions#using-a-specific-shell).
   This can lead issues such as multi-line scripts [not working as expected](https://github.com/ruby/setup-ruby/issues/13).
 * The `PATH` contains [multiple compiler toolchains](https://github.com/ruby/setup-ruby/issues/19). Use `where.exe` to debug which tool is used.
 * For Ruby ≥ 2.4, MSYS2 is prepended to the `Path`, similar to what RubyInstaller2 does.