Commit to ruby@2.6 support

Closes [hotwired#681][]

First, remove `ruby@3.0` syntax including `...` arguments and end-less
method definitions.

Next, add `ruby@2.6` and `ruby@2.7` to the CI matrix along with
`rails@7.1`.

[hotwired#681]: hotwired#681

.github/workflows/ci.yml

@@ -5,8 +5,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rails: [ "6.1", "7.0", "7.1" ]
-        ruby: [ "3.0", "3.1", "3.2", "3.3" ]
+        rails: [ "6.1", "7.0", "7.1", "7.2" ]
+        ruby: [ "2.6", "2.7", "3.0", "3.1", "3.2", "3.3" ]
         allow-fail: [ false ]
         include:
           - { ruby: "3.3",  rails: "main", allow-fail: true }

test/streams/streams_helper_test.rb

@@ -3,12 +3,16 @@
 class TestChannel < ApplicationCable::Channel; end
 
 class Turbo::StreamsHelperTest < ActionView::TestCase
-  class Component
+  Component = Struct.new(:id, :content) do
     extend ActiveModel::Naming
 
-    def initialize(id:, content:) = (@id, @content = id, content)
-    def render_in(...) = @content
-    def to_key = [@id]
+    def render_in(view_context)
+      content
+    end
+
+    def to_key
+      [id]
+    end
   end
 
   attr_accessor :formats