Stick with autoprefixer 8.x for now

Gemfile

@@ -38,7 +38,7 @@ gem "bootsnap", ">= 1.1.0", :require => false
 gem "r2", "~> 0.2.7"
 
 # Use autoprefixer to generate CSS prefixes
-gem "autoprefixer-rails"
+gem "autoprefixer-rails", "~> 8.6.3"
 
 # Use image_optim to optimise images
 gem "image_optim_rails"

Gemfile.lock

@@ -54,7 +54,7 @@ GEM
       rake (>= 10.4, < 13.0)
     arel (9.0.0)
     ast (2.4.0)
-    autoprefixer-rails (9.1.0)
+    autoprefixer-rails (8.6.5)
       execjs
     better_errors (2.4.0)
       coderay (>= 1.0.0)
@@ -382,7 +382,7 @@ DEPENDENCIES
   aasm
   actionpack-page_caching
   annotate
-  autoprefixer-rails
+  autoprefixer-rails (~> 8.6.3)
   better_errors
   bigdecimal (~> 1.1.0)
   binding_of_caller