Revert "ANDROID: vendor_hooks: add hook and OEM data for slab shrink"

This reverts commit bf769b72.

The hook android_vh_do_shrink_slab is not used by any vendor, so remove
it to help with merge issues with future LTS releases.

If this is needed by any real user, it can easily be reverted to add it
back and then the symbol should be added to the abi list at the same
time to prevent it from being removed again later.

Bug: 203756332
Bug: 188684131
Cc: rongqianfeng <rongqianfeng@vivo.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I814e3aad76770140063fad4a81951fc025b2b1dd