dataclasses: upgraded package to upstream

Upgraded dev-python/dataclasses to version 0.7 on amd64

This is required for black compatibility on Python 3.6.  Note the
package is in the Python standard library from 3.7 onwards, so we can
delete the package if we upgrade Python.

BUG=b:192389533
TEST=with follow-up, test black

Change-Id: Ibb1f600534d42f7eb4817682b0aea25816fa9666
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2998369
Tested-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
5 files changed