refactor: do not update ruby and bundler versions

.github/workflows/ruby.yml

@@ -9,7 +9,7 @@ name: Ruby
 
 on:
   push:
-    branches: [ "master" ]
+    branches: [ "ci" ]
   pull_request:
     branches: [ "master" ]
 
@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: ['3.1.2']
+        ruby-version: ['2.6', '2.7', '3.0']
 
     steps:
     - uses: actions/checkout@v3

Gemfile.lock

@@ -0,0 +1,36 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    colorize (0.8.1)
+    diff-lcs (1.3)
+    os (1.0.0)
+    psych (2.1.0)
+    rake (12.3.3)
+    rspec (3.5.0)
+      rspec-core (~> 3.5.0)
+      rspec-expectations (~> 3.5.0)
+      rspec-mocks (~> 3.5.0)
+    rspec-core (3.5.4)
+      rspec-support (~> 3.5.0)
+    rspec-expectations (3.5.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.5.0)
+    rspec-mocks (3.5.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.5.0)
+    rspec-support (3.5.0)
+
+PLATFORMS
+  ruby
+  x86-mingw32
+
+DEPENDENCIES
+  bundler
+  colorize
+  os
+  psych
+  rake
+  rspec
+
+BUNDLED WITH
+   1.15.4