Bump letter_opener_web from 1.4.1 to 2.0.0 (#16960)

Bumps [letter_opener_web](https://github.com/fgrehm/letter_opener_web) from 1.4.1 to 2.0.0.
- [Release notes](https://github.com/fgrehm/letter_opener_web/releases)
- [Changelog](https://github.com/fgrehm/letter_opener_web/blob/master/CHANGELOG.md)
- [Commits](https://github.com/fgrehm/letter_opener_web/compare/v1.4.1...v2.0.0)

---
updated-dependencies:
- dependency-name: letter_opener_web
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

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

Gemfile

@@ -130,7 +130,7 @@ group :development do
   gem 'binding_of_caller', '~> 1.0'
   gem 'bullet', '~> 6.1'
   gem 'letter_opener', '~> 1.7'
-  gem 'letter_opener_web', '~> 1.4'
+  gem 'letter_opener_web', '~> 2.0'
   gem 'memory_profiler'
   gem 'rubocop', '~> 1.23', require: false
   gem 'rubocop-rails', '~> 2.12', require: false