Reproduction steps:
1. Open my attached project ("case_863060");
2. Open the "main" scene
3. Open up a profiler or Task Manager
4. Enter play mode

Result: constantly rising memory usage.

This is caused by the "emission" sub-component of the particle system, as disabling it removes the memory leak.

Reproducible on: 5.5.0p3, 5.6.0b2
Not reproducible on: 5.4.4f1