[OpenJDK 2D-Dev] RFR: 8196288: Update src/java.desktop/share/legal/libharfbuzz.md for harfbuzz 1.7.1

[Phil Race]

bug: https://bugs.openjdk.java.net/browse/JDK-8196288
webrev: http://cr.openjdk.java.net/~prr/8196288/

This is a JDK10 doc-only fix.
The version is bumped to 1.7.1 and the (c) lines are adjusted to match
what is actually in the 1.7.1 COPYING file as approved by legal.

-phil.