Allow artifacts of the same name to be overwritten (#3509)

## Motivation and Context


## Description
After [upgrading to
actions/upload-artifact@v4](#3497),
it seems to have brought a behavior change where an artifact with the
same name is [disallowed by
default](https://github.com/smithy-lang/smithy-rs/actions/runs/8423689643/job/23067178393#step:4:639)
within a workflow run.

This happened during a
[release](https://github.com/smithy-lang/smithy-rs/blob/main/.github/workflows/release.yml)
workflow where it first invoked ci.yml (which then called
`generate-smithy-rs-release` and created an artifact with that action
name) and then called `generate-smithy-rs-release` by itself (attempted
to create an artifact with that action name again, leading to the error
above). This was not a problem previously when we were using
`actions/upload-artifact@v3`.

This PR explicitly sets `overwrite: true` to bring back the old behavior
for a place that's affected.

----

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choice._

Author: ysaito1001

.github/actions/docker-build/action.yml

@@ -66,3 +66,4 @@ runs:
       path: artifacts-${{ inputs.action }}.tar.gz
       if-no-files-found: error
       retention-days: 3
+      overwrite: true