RFR 8233799 (doc) Review the need for overview.html in the java.time package

[Roger Riggs]

Please review a trivial removal of a vestigal and unreferenced 
overview.html for java.time.
The same information had been incorporated into the package-info.java.
Nothing much to it just the removal of:
     src/java.base/share/classes/java/time/overview.html

Webrev:  http://cr.openjdk.java.net/~rriggs/webrev-overview-8233799/

Thanks, Roger