Update CI to Ruby 3.3, bump minimum Ruby to 3.1

Ruby 2.7 has been EOL since March 2023. The C extension tracing
behavior differs between Ruby 2.7 and modern Ruby (e.g. Class.new
call visibility in traces), causing all trace-output tests to fail.

- CI: Ruby 2.7 → 3.3, actions/checkout@v2 → v4
- Gemspec: required_ruby_version >= 2.7.0 → >= 3.1.0
- .ruby-version: 2.7.8 → 3.3.7

Author: phaselockedloop

.github/workflows/ci.yml

@@ -8,9 +8,9 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: ["2.7"]
+        ruby: ["3.3"]
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}
@@ -21,10 +21,10 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: ["2.7"]
+        ruby: ["3.3"]
     steps:
     - run: sudo apt-get update && sudo apt-get install -y valgrind
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}

.ruby-version

@@ -1 +1 @@
-2.7.8
+3.3.7

rotoscope.gemspec

@@ -21,7 +21,7 @@ Gem::Specification.new do |s|
   end
   s.metadata["allowed_push_host"] = "https://rubygems.org/"
 
-  s.required_ruby_version = ">= 2.7.0"
+  s.required_ruby_version = ">= 3.1.0"
   s.extensions = ["ext/rotoscope/extconf.rb"]
 
   s.add_development_dependency("minitest", "~> 5.0")