Refresh Ruby versions used for testing libdatadog gem

Added Ruby versions 3.2, 3.3 and 3.4, and removed old Rubies that I'm
about to drop on the next commit.

Author: ivoanjo

.github/workflows/test-ruby.yml

@@ -10,32 +10,11 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        ruby: [2.1, 2.3, 2.4, 2.5, 2.6, 2.7, '3.0', 3.1, head]
+        ruby: ['2.5', '2.6', '2.7', '3.0', '3.1', '3.2', '3.3', '3.4', head]
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # 4.2.2
-    - uses: ruby/setup-ruby@922ebc4c5262cd14e07bb0e1db020984b6c064fe # 1.226.0
-      with:
-        ruby-version: ${{ matrix.ruby }}
-        bundler-cache: true # runs 'bundle install' and caches installed gems automatically
-        working-directory: ruby/
-    - run: cd ruby && bundle exec rake
-  # Workaround for broken issue
-  # ```
-  # ERROR:  While executing gem ... (RuntimeError)
-  # Marshal.load reentered at marshal_load
-  # ```
-  # suggested in https://github.com/ruby/setup-ruby/issues/496 (use ubuntu 20.04 instead of a later version)
-  test-legacy-workaround:
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ubuntu-20.04]
-        ruby: [2.2]
-    runs-on: ${{ matrix.os }}
-    steps:
-    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # 4.2.2
-    - uses: ruby/setup-ruby@922ebc4c5262cd14e07bb0e1db020984b6c064fe # 1.226.0
+    - uses: ruby/setup-ruby@13e7a03dc3ac6c3798f4570bfead2aed4d96abfb # 1.244.0
       with:
         ruby-version: ${{ matrix.ruby }}
         bundler-cache: true # runs 'bundle install' and caches installed gems automatically