Update addressable.gemspec to link directly to versoned changelog

With this code it will generate this diff. And this link takes you
directly to the changelog.

--- a/addressable.gemspec
+++ b/addressable.gemspec
@@ -6,7 +6,7 @@ Gem::Specification.new do |s|
   s.version = "2.8.5"

   s.required_rubygems_version = Gem::Requirement.new(">= 0".freeze) if s.respond_to? :required_rubygems_version=
-  s.metadata = { "changelog_uri" => "https://github.com/sporkmonger/addressable/blob/main/CHANGELOG.md" } if s.respond_to? :metadata=
+  s.metadata = { "changelog_uri" => "https://github.com/sporkmonger/addressable/blob/addressable-2.8.5/CHANGELOG.md" } if s.respond_to? :metadata=
   s.require_paths = ["lib".freeze]
   s.authors = ["Bob Aman".freeze]
   s.date = "2023-08-03"

tasks/gem.rake

@@ -31,7 +31,7 @@ namespace :gem do
     s.homepage = "https://github.com/sporkmonger/addressable"
     s.license = "Apache-2.0"
     s.metadata = {
-      "changelog_uri" => "https://github.com/sporkmonger/addressable/blob/main/CHANGELOG.md"
+      "changelog_uri" => "https://github.com/sporkmonger/addressable/blob/addressable-#{PKG_VERSION}/CHANGELOG.md"
     }
   end