Add support for Ruby 3.2

Ruby 2.2 deprecated `File#exists?` in favor of `File#exist?`, and Ruby
3.2 removed the deprecated method.

We need to use the "new" method to run on Ruby 3.2.

Author: smortex

.github/workflows/ci.yml

@@ -18,6 +18,7 @@ jobs:
           - 2.7
           - 3.0
           - 3.1
+          - 3.2
       fail-fast: false
     steps:
       - uses: actions/checkout@v2
@@ -27,4 +28,4 @@ jobs:
           ruby-version: ${{ matrix.ruby-version }}
           bundler-cache: true
       - name: Run the test suite
-        run: bundle exec rake test
+        run: bundle exec rake test

lib/riemann/dash/browser_config/file.rb

@@ -7,7 +7,7 @@ def initialize(path)
   end
 
   def read
-    if ::File.exists? @path
+    if ::File.exist? @path
       ::File.open(@path, 'r') do |f|
         f.flock ::File::LOCK_SH
         f.read