Don't log error on success

Summary: std::map::erase(Key&) returns 0 on failure (key did not exist), 1 on success (key existed and was deleted). Prior to this change, PersistableBundle would log an error anytime a key was successfully deleted.

Test: added PersistableBundle test

Change-Id: I9c2f6cabd30f784d5dbde5dee1f3d0eb2461bd06
Signed-off-by: Abhishek Gadewar <abhishekgadewar@meta.com>