Fix RangeInfo RANGE_TYPE_PERCENT javadoc

When use RANGE_TYPE_PERCENT, the min, max, current have values from 0 to
100. Talkback uses this definition, and
java/com/google/android/accessibility/switchaccess/ui/VolumeSlider.java
also uses this definition, so it is better to change the javadoc.

Test: not needed for javadoc change
Change-Id: I895f1f045d7a3978104a7948a5964a33de15f1bd