Change mouse keys scroll rate

Earlier, the mouse keys scroll rate was too fast.
Changed mouse keys scroll rate from 1.0f -> 0.2f to improve scrolling
experience for the user.

Bug: 341799888
Test: Manual scrolling
Test: atest FrameworksServicesTests:MouseKeysInterceptorTest
Flag: EXEMPT bugfix
Change-Id: I58bf46102e2f1f4ab965ccb540f1de4388aba4ea