Build(deps): Bump bcrypt from 3.1.19 to 3.1.20

Bumps [bcrypt](https://github.com/codahale/bcrypt-ruby) from 3.1.19 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@v3.1.19...v3.1.20)

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

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile

@@ -87,7 +87,7 @@ gem 'pg', '~> 1.5.4'
 gem 'acts_as_versioned', git: 'https://github.com/mysociety/acts_as_versioned.git',
                          ref: '13e928b'
 gem 'active_model_otp'
-gem 'bcrypt', '~> 3.1.19'
+gem 'bcrypt', '~> 3.1.20'
 gem 'cancancan', '~> 3.5.0'
 gem 'charlock_holmes', '~> 0.7.7'
 gem 'dalli', '~> 3.2.6'

Gemfile.lock

@@ -153,7 +153,7 @@ GEM
       faraday (~> 0.9)
       faraday_middleware (~> 0.10)
       nokogiri (~> 1.6, >= 1.6.8)
-    bcrypt (3.1.19)
+    bcrypt (3.1.20)
     bindex (0.8.1)
     bootstrap-sass (2.3.2.2)
       sass (~> 3.2)
@@ -568,7 +568,7 @@ DEPENDENCIES
   annotate (< 3.2.1)
   aws-sdk-s3
   azure-storage
-  bcrypt (~> 3.1.19)
+  bcrypt (~> 3.1.20)
   bootstrap-sass (~> 2.3.2.2)
   bullet (~> 7.1.3)
   cancancan (~> 3.5.0)