before_install_linux.sh in rmagick-5.1.0 vs before_install_linux.sh in rmagick-5.2.0

@@ -1,9 +1,9 @@
 #!/usr/bin/env bash
 
 set -euox pipefail
 
-gem install bundler
+gem install bundler -v 2.3.26 # Bundler 2.4.x has dropped support for Ruby 2.3
 
 if [ -v STYLE_CHECKS ]; then
   set +ux
   exit 0
 fi