Rails 6: Clean coerced tests (#793)

* update AttributeMethodsTest tests

* clean AdapterTestWithoutTransaction coerce_tests! statement

* update CalculationsTest tests

* add coerced test for test_create_without_primary_key_no_extra_query

* remove test_relation_merging_with_merged_symbol_joins_is_aliased__coerced
fixed in rails/50684d15c6546d3050d93896612edd9c5a0fca62

* update test_sanitize_sql_like_example_use_case_coerced
updated in rails/de2f1e073b37f98a99334a909b8bc29f36ad506b

* remove coerce test_eager_loading_too_may_ids
fixed in #786

* remove fixed coerce test
test "column names are quoted when using #from clause and model has ignored columns" fixed in rails/d53b259a29e77a60a02e9c219661e19ef62ef9aa

* remove coerce NumericDataTest tests
tests been fiexd in active recorde

* updete ChangeSchemaTest coerce tests

* remove fixed test_scopes_honor_current_scopes_from_when_defined

* add tests comment

* clean lines spacing

* fix test_typecast_attribute_from_select_to_true_coerced

Author: YehudaGold