Update rubocop requirement from ~> 1.28.2 to ~> 1.50.2 (#454)

Updates the requirements on [rubocop](https://github.com/rubocop/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.28.2...v1.50.2)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/spec/image_spec.rb b/spec/image_spec.rb
index 437c950..f9bd2ea 100644
--- a/spec/image_spec.rb
+++ b/spec/image_spec.rb
@@ -32,12 +32,12 @@ describe 'Asciidoctor::Epub3::Converter - Image' do
 
   it 'does not duplicate images in manifest' do
     book, = to_epub fixture_file('inline-image/book.adoc')
-    expect(book.items.keys.select {|k| k.include? 'wolpertinger' }.size).to eq(1)
+    expect(book.items.keys.select { |k| k.include? 'wolpertinger' }.size).to eq(1)
   end
 
   it 'does not add data-uri images to manifest' do
     book, = to_epub fixture_file('inline-image/book.adoc'), attributes: { 'data-uri' => '' }
-    expect(book.manifest.items.select {|_, v| v.href.start_with? 'data:' }).to be_empty
+    expect(book.manifest.items.select { |_, v| v.href.start_with? 'data:' }).to be_empty
   end
 
   it 'converts font-based icons to CSS' do