Fix javadocs based on recent case consistency change

Commit a40d2447b6f516116135ee7f126579771ba98a2c made the
case consistently "as for the beginning of a sentence".
This updates the docs to reflect that. Previously the
result depended on the string returned (e.g. "Tomorrow"
was capitalized in English) and the casing varied
within and between locales.

Bug: 20247811
(cherry-picked from commit 0e1c0e11)

Change-Id: I7b48958725b32b13bee00347585472f8073e7761