dont use unless and else, per rubocop

lib/jekyll-seo-tag/drop.rb

@@ -183,10 +183,10 @@ module Jekyll
 
       def canonical_url
         @canonical_url ||= begin
-          unless page["canonical_url"].to_s.empty?
-            page["canonical_url"]
-          else
+          if page["canonical_url"].to_s.empty?
             filters.absolute_url(page["url"]).to_s.gsub(%r!/index\.html$!, "/")
+          else
+            page["canonical_url"]
           end
         end
       end

spec/jekyll_seo_tag/drop_spec.rb

@@ -638,7 +638,6 @@ RSpec.describe Jekyll::SeoTag::Drop do
     end
 
     context "when canonical url is not specified for a page" do
-
       it "uses site specific canonical url" do
         expect(subject.canonical_url).to eq("http://example.com/page.html")
       end