Add "default subscriber profile" to the XML example in the README

[kenichiice]

When I try the talker/listener example in the README, I get the following error message.

$ FASTRTPS_DEFAULT_PROFILES_FILE=test.xml RMW_FASTRTPS_USE_QOS_FROM_XML=1 RMW_IMPLEMENTATION=rmw_fastrtps_cpp ros2 run demo_nodes_cpp talker
2023-01-24 11:18:49.428 [RTPS_READER_HISTORY Error] Change payload size of '60' bytes is larger than the history payload size of '35' bytes and cannot be resized. -> Function can_change_be_added_nts
2023-01-24 11:18:49.429 [RTPS_READER_HISTORY Error] Change payload size of '84' bytes is larger than the history payload size of '35' bytes and cannot be resized. -> Function can_change_be_added_nts
...

$ FASTRTPS_DEFAULT_PROFILES_FILE=test.xml RMW_FASTRTPS_USE_QOS_FROM_XML=1 RMW_IMPLEMENTATION=rmw_fastrtps_cpp ros2 run demo_nodes_cpp listener
2023-01-24 11:22:27.736 [RTPS_READER_HISTORY Error] Change payload size of '64' bytes is larger than the history payload size of '35' bytes and cannot be resized. -> Function can_change_be_added_nts
2023-01-24 11:22:27.737 [RTPS_READER_HISTORY Error] Change payload size of '88' bytes is larger than the history payload size of '35' bytes and cannot be resized. -> Function can_change_be_added_nts
...

Adding "default subscriber profile" to XML works, so I created such a pull request.

The default subscriber profile seems to have been lost in the 1853a8397560f867187741ae5a1306c9918cabbd.

[fujitatomoya]

with @MiguelCompany approval, i will go ahead to merge this.

[fujitatomoya]

This needs to be backport to humble.

[fujitatomoya]

@Mergifyio backport humble

[mergify[bot]]

backport humble

✅ Backports have been created

* [#664 Add "default subscriber profile" to the XML example in the README (backport #663)](https://github.com/ros2/rmw_fastrtps/pull/664) has been created for branch `humble`

[fujitatomoya]

@kenichiice thank you very much for the contribution.