PostgreSQL 10 converts unknown type to text type

Commit 1a5d9399 removed the "Profiling Rails Applications" guide
but the YAML entry for this guide wasn't.

[ci skip]

Remove redundant `assert_nothing_raised` before another assertions

- Rename test cases from  `unknown` to `unrecognized` since unknown OID
is one of possible unrecognized types by Rails

- Use "select 'pg_catalog.pg_class'::regclass" whose OID is 2205, which
will not be converted to recognized type in PostgreSQL 10.

activerecord_unittest=# select oid, typname from pg_type where oid in (2205, 2277);
 oid  | typname
------+----------
 2205 | regclass
 2277 | anyarray
(2 rows)

Addresses #28868

Fix `test_pluck_without_column_names` when using Oracle

Remove html tag making markdown misrender [ci skip]

These `assert_nothing_raised` are covered by following assertions.

Testing `ReservedWordTest` for all adapters

Other examples were removed in 53ff5fc6

[ci skip]

`ReservedWordTest` expects that any identifiers are quoted properly.
It should be tested for all adapters.

Remove assert_nothing_raised, as test is already testing the required concerns

load_schema! is overridden by attribute modules, so we need to wait
until it has returned.

Introduce mattr_accessor default option

Don't create extra assignment, just return

Fix typo on error message when route definition is ambiguous.

Fix formatting of `direct` and `resolve` doc [ci skip]

Change default application.js included in new Rails app [ci skip]

Remove a redundant default_scope tests

Make Rails welcome page responsive

[ci skip] Fix `scaffold_controller` generator usage

some typos and rephrasing in system test guide [ci skip]

Document support for composite primary keys

Prevent making bind param if casted value is nil