Revert "Protect PostIt deletion by SolarMutex."

Probably there is a more prosaic explanation; though I am unable to reproduce
now whatever I try - with or without the patch.

This reverts commit 2b2c528826b6b29d90fcb6a8e755c75cb0d65985.

Change-Id: Ia3c1017f27d28bc228c497f34b8777b487d54fb4