Update actions/checkout action to v4 (#45)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/gem-push.yml

@@ -15,7 +15,7 @@ jobs:
       packages: write
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Set up Ruby 3.0
       uses: ruby/setup-ruby@360dc864d5da99d54fcb8e9148c14a84b90d3e88
       with:

.github/workflows/ruby.yml

@@ -22,7 +22,7 @@ jobs:
         ruby-version: ['3.0']
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Set up Ruby
     # To automatically get bug fixes and new Ruby versions for ruby/setup-ruby,
     # change this to (see https://github.com/ruby/setup-ruby#versioning):
@@ -48,7 +48,7 @@ jobs:
 
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Set up Ruby
     # To automatically get bug fixes and new Ruby versions for ruby/setup-ruby,
     # change this to (see https://github.com/ruby/setup-ruby#versioning):