Remove if current_adapter?(:PostgreSQLAdapter)

because Active Record `bin/test` only executes its own adapter tests.
Test files under `test/cases/adapters` directory does not have to
say `if current_adapter?` anymore.

activerecord/test/cases/adapters/postgresql/datatype_test.rb

@@ -7,7 +7,7 @@ class PostgresqlTime < ActiveRecord::Base
   # Declare attributes to get rid from deprecation warnings on ActiveRecord 6.1
   attribute :time_interval,        :string
   attribute :scaled_time_interval, :interval
-end if current_adapter?(:PostgreSQLAdapter)
+end
 
 class PostgresqlOid < ActiveRecord::Base
 end

activerecord/test/cases/adapters/postgresql/geometric_test.rb

@@ -16,7 +16,7 @@ class PostgresqlPoint < ActiveRecord::Base
     attribute :legacy_x, :legacy_point
     attribute :legacy_y, :legacy_point
     attribute :legacy_z, :legacy_point
-  end if current_adapter?(:PostgreSQLAdapter)
+  end
 
   def setup
     @connection = ActiveRecord::Base.connection

activerecord/test/cases/adapters/postgresql/interval_test.rb

@@ -12,7 +12,7 @@ class IntervalDataType < ActiveRecord::Base
     attribute :default_term, :interval
     attribute :all_terms,    :interval, array: true
     attribute :legacy_term,  :string
-  end if current_adapter?(:PostgreSQLAdapter)
+  end
 
   class DeprecatedIntervalDataType < ActiveRecord::Base; end