Set a title for personal dictionary

After the collapsing toolbar layout is applied to subsetting pages, the
title of the personal dictionary page won't be shown. This CL is to set
a title for the personal dictionary page.

Bug: 176897229
Test: manual test and visual verified
1) Navigate to Settings -> System -> Languages & input -> Personal
dictionary
2) Enable collapsing toolbar feature
3) Observe and check if the title is shown as normal

Change-Id: I0b6488bc2c8040b275ba0d5348d09aa4bad905d1