gems: remove ffi-geos

We don't need it now that we don't link to a compiled geos version
anymore.

Gemfile

@@ -24,7 +24,6 @@ gem 'devise-i18n'
 gem 'devise-two-factor', github: 'jason-hobbs/devise-two-factor', branch: 'master' # Rails 6.1 compatibility: https://github.com/tinfoil/devise-two-factor/issues/183
 gem 'discard'
 gem 'dotenv-rails', require: 'dotenv/rails-now' # dotenv should always be loaded before rails
-gem 'ffi-geos', require: false
 gem 'flipper'
 gem 'flipper-active_record'
 gem 'flipper-ui'

Gemfile.lock

@@ -255,8 +255,6 @@ GEM
       ruby2_keywords
     faraday-net_http (1.0.1)
     ffi (1.14.2)
-    ffi-geos (2.1.0)
-      ffi (>= 1.0.0)
     flipper (0.20.3)
     flipper-active_record (0.20.3)
       activerecord (>= 5.0, < 7)
@@ -843,7 +841,6 @@ DEPENDENCIES
   discard
   dotenv-rails
   factory_bot
-  ffi-geos
   flipper
   flipper-active_record
   flipper-ui