GitHub Actions parses 3.0 as '3', so use quotes

* And adapt excludes.

Author: eregon

.github/workflows/test.yml

@@ -17,17 +17,17 @@ jobs:
       matrix:
         os: [ ubuntu-16.04, ubuntu-18.04, ubuntu-20.04, macos-10.15, macos-11.0, windows-2016, windows-2019 ]
         # Use various version syntax here for testing
-        ruby: [ 2.1, 2.2, 2.3, 2.4, 2.5, 2.6.6, 2.7, 3.0, ruby-head, debug, jruby-9.1, jruby, jruby-head, truffleruby, truffleruby-head ]
+        ruby: [ 2.1, 2.2, 2.3, 2.4, 2.5, 2.6.6, 2.7, '3.0', ruby-head, debug, jruby-9.1, jruby, jruby-head, truffleruby, truffleruby-head ]
         include:
         - { os: windows-2016, ruby: mingw }
         - { os: windows-2019, ruby: mingw }
         - { os: windows-2019, ruby: mswin }
         exclude:
-        - { os: windows-2016, ruby: ruby-3.0.0-preview1 }
+        - { os: windows-2016, ruby: '3.0' }
         - { os: windows-2016, ruby: debug }
         - { os: windows-2016, ruby: truffleruby }
         - { os: windows-2016, ruby: truffleruby-head }
-        - { os: windows-2019, ruby: ruby-3.0.0-preview1 }
+        - { os: windows-2019, ruby: '3.0' }
         - { os: windows-2019, ruby: debug }
         - { os: windows-2019, ruby: truffleruby }
         - { os: windows-2019, ruby: truffleruby-head }