fix: specify bundler version in setup-ruby action

Use the 'bundler' parameter in ruby/setup-ruby action to install
bundler 2.3 for Ruby 2.7 and default for Ruby 3.4, preventing
the automatic installation of incompatible bundler 2.6.6.

Author: RomKadria

.github/workflows/ci.yml

@@ -25,21 +25,17 @@ jobs:
         with:
           ruby-version: ${{ matrix.ruby }}
           bundler-cache: false
-
-      - name: Install compatible bundler for Ruby 2.7
-        if: matrix.ruby == '2.7'
-        run: |
-          gem install bundler -v '~> 2.3.0'
-          bundle config set --local path 'vendor/bundle'
-          bundle config set --local frozen false
-          bundle update --bundler
+          bundler: ${{ matrix.ruby == '2.7' && '2.3' || 'default' }}
 
       - name: Configure bundler
-        if: matrix.ruby != '2.7'
         run: |
           bundle config set --local path 'vendor/bundle'
           bundle config set --local frozen false
 
+      - name: Update bundler in lockfile for Ruby 2.7
+        if: matrix.ruby == '2.7'
+        run: bundle update --bundler
+
       - name: Install dependencies
         run: bundle install
 
@@ -63,21 +59,17 @@ jobs:
         with:
           ruby-version: ${{ matrix.ruby }}
           bundler-cache: false
-
-      - name: Install compatible bundler for Ruby 2.7
-        if: matrix.ruby == '2.7'
-        run: |
-          gem install bundler -v '~> 2.3.0'
-          bundle config set --local path 'vendor/bundle'
-          bundle config set --local frozen false
-          bundle update --bundler
+          bundler: ${{ matrix.ruby == '2.7' && '2.3' || 'default' }}
 
       - name: Configure bundler
-        if: matrix.ruby != '2.7'
         run: |
           bundle config set --local path 'vendor/bundle'
           bundle config set --local frozen false
 
+      - name: Update bundler in lockfile for Ruby 2.7
+        if: matrix.ruby == '2.7'
+        run: bundle update --bundler
+
       - name: Install base dependencies
         run: bundle install
 
@@ -107,21 +99,17 @@ jobs:
         with:
           ruby-version: ${{ matrix.ruby }}
           bundler-cache: false
-
-      - name: Install compatible bundler for Ruby 2.7
-        if: matrix.ruby == '2.7'
-        run: |
-          gem install bundler -v '~> 2.3.0'
-          bundle config set --local path 'vendor/bundle'
-          bundle config set --local frozen false
-          bundle update --bundler
+          bundler: ${{ matrix.ruby == '2.7' && '2.3' || 'default' }}
 
       - name: Configure bundler
-        if: matrix.ruby != '2.7'
         run: |
           bundle config set --local path 'vendor/bundle'
           bundle config set --local frozen false
 
+      - name: Update bundler in lockfile for Ruby 2.7
+        if: matrix.ruby == '2.7'
+        run: bundle update --bundler
+
       - name: Install base dependencies
         run: bundle install