Drop sqlite3

We should spec on the database we use...

.github/workflows/next-rails.yml

@@ -12,7 +12,6 @@ jobs:
     runs-on: ubuntu-latest
     name: next-rails
     env:
-      OSEM_DB_ADAPTER: sqlite3
       RAILS_ENV: test
     strategy:
       matrix:

.github/workflows/spec.yml

@@ -25,7 +25,6 @@ jobs:
     runs-on: ubuntu-latest
     name: spec
     env:
-      OSEM_DB_ADAPTER: sqlite3
       RAILS_ENV: test
     strategy:
       matrix:

Gemfile

@@ -248,8 +248,6 @@ end
 group :development, :test do
   # as debugger
   gem 'byebug'
-  # as development/test database
-  gem 'sqlite3'
   # to test new rails version
   gem 'next_rails'
 end

Gemfile.lock

@@ -556,8 +556,6 @@ GEM
       actionpack (>= 5.2)
       activesupport (>= 5.2)
       sprockets (>= 3.0.0)
-    sqlite3 (1.7.3)
-      mini_portile2 (~> 2.8.0)
     ssrf_filter (1.1.2)
     stripe (5.55.0)
     stripe-ruby-mock (3.1.0)
@@ -703,7 +701,6 @@ DEPENDENCIES
   simplecov-cobertura
   skylight
   sprockets-rails
-  sqlite3
   stripe
   stripe-ruby-mock (~> 3.1.0.rc3)
   timecop