SQLite2Adapter doesn't exist

Signed-off-by: José Valim <jose.valim@gmail.com>

activerecord/test/cases/migration_test.rb

@@ -1019,7 +1019,7 @@ def test_add_table_with_decimals
       # This one is fun. The 'value_of_e' field is defined as 'DECIMAL' with
       # precision/scale explicitly left out.  By the SQL standard, numbers
       # assigned to this field should be truncated but that's seldom respected.
-      if current_adapter?(:PostgreSQLAdapter, :SQLite2Adapter)
+      if current_adapter?(:PostgreSQLAdapter)
         # - PostgreSQL changes the SQL spec on columns declared simply as
         # "decimal" to something more useful: instead of being given a scale
         # of 0, they take on the compile-time limit for precision and scale,