linux-pipewire: Remove extra loop teardown

[kkartaltepe]

Description

pw_thread_loop_wait must be called with the lock held, so this code was throwing warnings on newer pipewire libraries. With it removed there seems to be no reason to perform a stop before destroying the loop which will internally call stop since at least 7 years ago.

https://gitlab.freedesktop.org/pipewire/pipewire/-/blame/d0a2e6316bb652b064db8f2ff63b86afd52bddfb/src/pipewire/thread-loop.c#L247

Motivation and Context

No more pipewire warnings on shutdown.

How Has This Been Tested?

Test scene shutsdown fine still.

Types of changes

• Code cleanup (non-breaking change which makes code smaller or more readable)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.