Update sqlite3 requirement from ~> 1.4 to ~> 2.0 (#311)

Updates the requirements on [sqlite3](https://github.com/sparklemotion/sqlite3-ruby) to permit the latest version.
- [Release notes](https://github.com/sparklemotion/sqlite3-ruby/releases)
- [Changelog](https://github.com/sparklemotion/sqlite3-ruby/blob/main/CHANGELOG.md)
- [Commits](sparklemotion/sqlite3-ruby@v1.4.0...v2.0.1)

---
updated-dependencies:
- dependency-name: sqlite3
  dependency-type: direct:development
...

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Author: dependabot[bot]

impressionist.gemspec

@@ -25,5 +25,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'bundler', '~> 2.0'
   s.add_development_dependency 'capybara'
   s.add_development_dependency 'rspec-rails'
-  s.add_development_dependency 'sqlite3', '~> 1.4'
+  s.add_development_dependency 'sqlite3', '~> 2.0'
 end