dev-go/go-tools: Update the ebuild version to close to upstream version.

ChromeOS team suggested to keep the go-tools ebuild version to be close
to what tag we are using from upstream. We use v0.3.1 version from
go-tools repository but there is no tag associated with it. However, the
closet tag present is v0.3.0 and the commit we use is based on top of
v0.3.0 tag.

BUG=b/267649872
TEST=presubmit
RELEASE_NOTE=None

Change-Id: I1dc6e24ac169ed0859113a7cce52443d25d32ce9
Reviewed-on: https://cos-review.googlesource.com/c/third_party/overlays/chromiumos-overlay/+/42791
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>
3 files changed