Remove english model from being a required module

Removes english model from being a required module for
libtextclassifier.
OEMs may choose to factory install any set of modules.
ConfigUpdateInstallReceiver can also be used to push an updatable
model to a device.

Test: Checked that a new build does not bundle an english model by
default.

Bug: 64746048

Change-Id: I824accf3ac115c00797f1c6bc0904e34b1c5d46c