build: completely remove no_assert option

*This is not needed anymore with the following patch
 https://github.com/AOKP/build/commit/93068fd32f2794527476fa7ce4cb7c823229ae65
 The above patch allows device asserts to be defined in the boardconfig.
 If no asserts are wanted, not adding TARGET_OTA_ASSERT_DEVICE to
 boardconfig will accomplish this. Furthermore, the no_assert option
 conflicts with the patch to define asserts in boardconfig. Removing fixes
 our ability to define asserts for devices. So this kills two birds with
 one stone. Wutang.

Change-Id: I41f9e6c4e09725002544b59287f8aeecb2dad894
Signed-off-by: Jonathan Steadman <xxwhitehawk@gmail.com>