Enable running stubtest on more of types-pika (#9826)

Make aliases for non-imported dependency private

stubs/pika/@tests/stubtest_allowlist.txt

@@ -2,11 +2,6 @@
 pika.compat.StringIO.seek
 pika.compat.StringIO.truncate
 
-# Requires external libraries to be installed.
-pika\.adapters\.gevent_connection.*
-pika\.adapters\.tornado_connection.*
-pika\.adapters\.twisted_connection.*
-
 # Stubtest doesn't understand that a property alias is also read-only.
 pika.BlockingConnection.basic_nack
 pika.BlockingConnection.consumer_cancel_notify