Lock Bundler to v2.3.26

This is the last version that supports Ruby 2.4 and 2.5.

Author: andyundso

.circleci/config.yml

@@ -112,7 +112,7 @@ jobs:
           command: |
             $Env:PATH = "C:\\Ruby<< parameters.ruby_version >>-x64\\bin;$Env:PATH"
             ridk install 2
-            gem install bundler
+            gem install bundler -v 2.3.26
 
       - checkout