Bump bcrypt from 3.1.18 to 3.1.20

Bumps [bcrypt](https://github.com/codahale/bcrypt-ruby) from 3.1.18 to 3.1.20.
- [Release notes](https://github.com/codahale/bcrypt-ruby/releases)
- [Changelog](https://github.com/bcrypt-ruby/bcrypt-ruby/blob/master/CHANGELOG)
- [Commits](bcrypt-ruby/bcrypt-ruby@v3.1.18...v3.1.20)

---
updated-dependencies:
- dependency-name: bcrypt
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -22,7 +22,7 @@ GEM
     ast (2.4.2)
     backports (3.23.0)
     base64 (0.2.0)
-    bcrypt (3.1.18)
+    bcrypt (3.1.20)
     bigdecimal (3.1.7)
     brakeman (6.1.2)
       racc