Bump ffi from 1.15.5 to 1.16.3

Gemfile

@@ -50,7 +50,7 @@ gem 'rails_same_site_cookie', { git: "https://github.com/alphagov/rails-same-sit
 
 # Gem ffi in Ruby 2.6.6 requires a version of the system library `/usr/lib/libffi.dylib` that's not available on MacOS Mojave.
 # Revert the gem to a previous version that works with the library available on our dev machines.
-gem 'ffi', '1.15.5'
+gem 'ffi', '1.16.3'
 
 group :development do
   # Access an IRB console on exception pages or by using <%= console %> in views

Gemfile.lock

@@ -115,7 +115,7 @@ GEM
     faraday-patron (1.0.0)
     faraday-rack (1.0.0)
     faraday-retry (1.0.3)
-    ffi (1.15.5)
+    ffi (1.16.3)
     ffi-compiler (1.0.1)
       ffi (>= 1.0.0)
       rake
@@ -376,7 +376,7 @@ DEPENDENCIES
   connection_pool
   dotenv-rails
   email_validator (~> 1.6)
-  ffi (= 1.15.5)
+  ffi (= 1.16.3)
   headless
   http (~> 5.1.1)
   jasmine