Update dependency oats to v0.4.0 (#191)

| datasource      | package      | from   | to     |
| --------------- | ------------ | ------ | ------ |
| github-releases | grafana/oats | v0.3.2 | v0.4.0 |

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/oats.yml

@@ -70,7 +70,7 @@ jobs:
       - name: Install OATS
         env:
           # renovate: datasource=github-releases depName=oats packageName=grafana/oats
-          OATS_VERSION: v0.3.2
+          OATS_VERSION: v0.4.0
         run: go install "github.com/grafana/oats@${OATS_VERSION}"
 
       - name: Run acceptance tests