Disable text length assert in LoginActivityTest#testNewTextAttributes.

Security fix a0c6539 limits the text length 5000. We cannot change
assert condition to 5000 because it will break 1st R release. Disable
text length assert in this test case.

Bug: 166206311
Test: atest android.autofillservice.cts.LoginActivityTest#\
testNewTextAttributes

Merged-In: Ic4ea0206887633d4b6657e18c72d3495ce3685b7
Change-Id: I0b7b53535a7c88c43b64af191ce30f6bfba8f059