docs(changelog): fix broken version bumping

Standard Version was not bumping the package metadata files as it
should have been. It's not clear to me why, but there is an open
[GitHub issue][1] for documenting this behaviour.

[1]: https://github.com/conventional-changelog/standard-version/issues/506



Change-Id: Ie89a81272fe507a3d2e1cd33c6ac1bdcc8ac3d75
Signed-off-by: Chris Kay <chris.kay@arm.com>