Avoid spurious keyword argument warning on Ruby 2.7

[jeremyevans]

There is no reason to use **kwargs in either of these methods,
as connect_start doesn't handle keywords (keywords passed to it
will be treated as a positional hash).

Fixes deprecation warning when using Sequel's postgres adapter in
Ruby 2.7.

[stanhu]

Actually, I'm seeing this warning in 1.4.0 now:

DEPRECATION WARNING: /Users/stanhu/.asdf/installs/ruby/2.7.5/lib/ruby/gems/2.7.0/gems/pg-1.4.0/lib/pg.rb:69: warning: Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call
/Users/stanhu/.asdf/installs/ruby/2.7.5/lib/ruby/gems/2.7.0/gems/pg-1.4.0/lib/pg/connection.rb:660: warning: The called method `new' is defined here

This may be coming from Rails v6.1.4.7:

(byebug) bt
--> #0  #<Class:PG::Connection>.new(*args#Array, kwargs#Hash) at /Users/stanhu/.asdf/installs/ruby/2.7.5/lib/ruby/gems/2.7.0/gems/pg-1.4.0/lib/pg/connection.rb:663
    #1  #<Class:PG>.connect(*args#Array, &block#NilClass) at /Users/stanhu/.asdf/installs/ruby/2.7.5/lib/ruby/gems/2.7.0/gems/pg-1.4.0/lib/pg.rb:69
    #2  #<Class:ActiveRecord::ConnectionAdapters::PostgreSQLAdapter>.new_client(conn_params#Hash) at /Users/stanhu/.asdf/installs/ruby/2.7.5/lib/ruby/gems/2.7.0/gems/activerecord-6.1.4.7/lib/active_record/connection_adapters/postgresql_adapter.rb:78

Which seems to be fixed via rails/rails@c3a0e32.

[jeremyevans]

This pull request to fix the issue was correct. This issue was reintroduced in 6d61d3d. It seems broken unnecessarily, since the **kwargs are not even used by new, just passed to connect_to_hosts, which only accepts *args. I'll send another pull request to fix this new issue.