fix(non linear font scaling): fix test from timing out.

Reduce number of fractions tested by an order of magnitude. Instead use
fuzzed random numbers to test.

Fix: 270054472
Test: atest FrameworksCoreTests:android.content.res.FontScaleConverterFactoryTest
Change-Id: Ifffee2e9c33e81152d5e6b9a1b7ad77e925a48c7