Allow "sqlite3" as ENV["DB"]

Since solidus-orbs-extension v0.10.0, the CI runner will set the ENV var
for sqlite to be `sqlite3`, which currently raises an error.

(cherry picked from commit 8070485)

core/lib/generators/spree/dummy/templates/rails/database.yml

@@ -3,7 +3,7 @@
           'mysql'
         when 'postgres', 'postgresql'
           'postgres'
-        when 'sqlite', '', nil
+        when /sqlite3?/, '', nil
           'sqlite'
         else
           raise "Invalid DB specified: #{ENV['DB']}"