ci: Use bundler-cache instead of manual Bundler install

* ci: Use bundler-cache instead of manual Bundler install

Let ruby/setup-ruby manage Bundler and dependency installation.
This avoids the manual Bundler install step and handles version
differences more reliably.

* ci: Use "latest" Bundler with Ruby "head"

Prevents picking up of the Gemfile's v2.4.22 which is no longer compatible with
Ruby 4.

* ci: Pin old Bundler for Ruby 2.7 and release others

This inverts the dependency strategy and within the CI matrix allows everything
to use the latest except for Ruby 2.7 which is known to fail with later Bundler
versions.

Author: tokengeek

.github/workflows/ruby.yml

@@ -22,6 +22,9 @@ jobs:
       fail-fast: false
       matrix:
         ruby: ["2.7", "3.0", "3.1", "3.2", "3.3", "head"]
+        include:
+          - ruby: "2.7"
+            bundler: "2.4.22"
     env:
       DEBUG: "true"
     steps:
@@ -32,9 +35,7 @@ jobs:
       uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}
-    - name: Install Bundler
-      run: gem install bundler -v $(grep -A 1 "BUNDLED WITH" Gemfile.lock | tail -n 1 | awk '{print $1}')
-    - name: Install dependencies
-      run: bundle install
+        bundler: ${{ matrix.bundler || 'default' }}
+        bundler-cache: true
     - name: Run tests
       run: bundle exec rake

Gemfile.lock

@@ -132,6 +132,3 @@ DEPENDENCIES
   simplecov
   vcr (~> 2.5)
   webmock
-
-BUNDLED WITH
-   2.4.22