dir/inprocess: make Delete Watch Entry contain the next sequence
dir/inprocess: make Delete Watch Entry contain the next sequence

The current code incremented the sequence number but didn't
use it in the watch entry.

Change-Id: I8000f31bcd991835eba684e7aaf401e69d494a07
Reviewed-on: https://upspin-review.googlesource.com/17280
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

upspin/upspin,upspin/upspin