Use a specific Bundler version to match the required version of Ruby we need.

Author: armiol

.github/workflows/check-code-embedding.yml

@@ -36,8 +36,14 @@ jobs:
         with:
           ruby-version: '2.7.4'
 
+      # Bundler version is restricted to `2.4.22`,
+      # as we want to use Ruby `2.7.4` to match GH Pages environment.
+      #
+      # Any newer versions of Bundler require Ruby 3.x,
+      # which are much newer than what's GH Pages has at the moment.
+      #
       - run: |
-          gem install bundler
+          gem install bundler -v 2.4.22
           bundle install
 
       - name: Check Embedding

.github/workflows/proof-links.yml

@@ -21,9 +21,15 @@ jobs:
         with:
           ruby-version: '2.7.4'
 
+      # Bundler version is restricted to `2.4.22`,
+      # as we want to use Ruby `2.7.4` to match GH Pages environment.
+      #
+      # Any newer versions of Bundler require Ruby 3.x,
+      # which are much newer than what's GH Pages has at the moment.
+      #
       - name: Run Jekyll build
         run: |
-          gem install bundler
+          gem install bundler -v 2.4.22
           bundle install
           bundle exec jekyll build