Update sqlite3 requirement from ~> 1.4.1 to ~> 1.6.0

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/master/CHANGELOG.md)
- [Commits](sparklemotion/sqlite3-ruby@v1.4.1...v1.6.0)

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

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

Author: dependabot[bot]

gemfiles/Gemfile.additional

@@ -10,7 +10,7 @@ gem "httpclient"
 gem "rexml"
 gem "sequel", "> 0"
 gem "sidekiq"
-gem "sqlite3", "~> 1.4.1"
+gem "sqlite3", "~> 1.6.0"
 gem "tilt"
 gem "haml"
 gem "redis"