Use Xcode 13.4.1 in CI

Author: mokagio

.buildkite/pipeline.yml

@@ -3,7 +3,7 @@ common_params:
   plugins: &common_plugins
   - &bash_cache automattic/bash-cache#2.0.0: ~
   env: &common_env
-    IMAGE_ID: xcode-13
+    IMAGE_ID: xcode-13.4.1
 
 # This is the default pipeline – it will build and test the pod
 steps:
@@ -14,7 +14,7 @@ steps:
     key: "test"
     command: |
       # See https://github.com/Automattic/bash-cache-buildkite-plugin/issues/16
-      gem install bundler:2.3.4
+      gem install bundler
       build_and_test_pod
     env: *common_env
     plugins: *common_plugins
@@ -26,7 +26,7 @@ steps:
     key: "validate"
     command: |
       # See https://github.com/Automattic/bash-cache-buildkite-plugin/issues/16
-      gem install bundler:2.3.4
+      gem install bundler
       validate_podspec
     env: *common_env
     plugins: *common_plugins
@@ -38,7 +38,7 @@ steps:
     key: "lint"
     command: |
       # See https://github.com/Automattic/bash-cache-buildkite-plugin/issues/16
-      gem install bundler:2.3.4
+      gem install bundler
       lint_pod
     env: *common_env
     plugins: *common_plugins