HAVE_RB_EXT_RACTOR_SAFE is already defined on ruby-head

Author: mrkn

.github/workflows/ci.yml

@@ -18,7 +18,6 @@ jobs:
         - macos-10.15
         - windows-latest
         ruby:
-        - 3.0.0-preview2
         - 2.7
         - 2.6
         - 2.5
@@ -29,7 +28,6 @@ jobs:
         - { os: windows-latest , ruby: mingw }
         - { os: windows-latest , ruby: mswin }
         exclude:
-        - { os: windows-latest , ruby: 3.0.0-preview2 }
         - { os: windows-latest , ruby: debug }
 
     steps:

ext/digest/extconf.rb

@@ -8,6 +8,4 @@
   "digest.h" => "$(HDRDIR)"
 }
 
-have_func("rb_ext_ractor_safe")
-
 create_makefile("digest")