fix: don't detach threads (#6333)

Previously, we would detach threads that did not exit in a reasonable
time, meaning they'd continue running and potentially accessing data
that had been freed, causing us to crash.
With this change, we _dont_ detach the thread, and let the thread
destructor do as it pleases (which will be terminating).
Neither solution is clean - old solution would sometimes work, but this
should give us a better indicator of where we're doing things wrong.

src/controllers/sound/MiniaudioBackend.cpp

@@ -235,7 +235,6 @@ MiniaudioBackend::~MiniaudioBackend()
 
         qCWarning(chatterinoSound)
             << "Audio thread did not stop within 1 second";
-        this->audioThread->detach();
     }
 }