Refrain from re-writing xml after package removal

This CL removes the logic to rewrite shortcuts.xml after a package
removal.

Historically all shortcuts were persisted in a single file, which
implies the file needs to be updated after a package is removed. This is
no longer the case since afrer ag/11301492 shortcuts from each
individual package are splitted into separate files, corresponding xml
is removed along with the package, so a re-write is not necessary.

For shortcuts that are pinned to launcher, these shortcuts are persisted
to xml file only during backup. We don't currently update that xml
during package removal.


Bug: 195994150
Test: atest ShortcutManagerTest1 ShortcutManagerTest2 ShortcutManagerTest3 ShortcutManagerTest4 ShortcutManagerTest5 ShortcutManagerTest6 ShortcutManagerTest7 ShortcutManagerTest8 ShortcutManagerTest9 ShortcutManagerTest10 ShortcutManagerTest11
Test: atest CtsShortcutManagerTestCases
Change-Id: I2283b7b3ce9cb157e7cc4a9f2a0de168a5ce8b72