[13] RFR: 8228450: unicode.md and icu.md text should be pre-formatted

[naoto.sato at oracle.com]

Hi,

Please review this doc only fix to the following issue:

https://bugs.openjdk.java.net/browse/JDK-8228450

The proposed changeset is located at:

http://cr.openjdk.java.net/~naoto/8228450/webrev.00/

This is simply to supply triple back ticks (```) in the .md files so 
that the text will not be formatted on HTML conversion.

Naoto