docker: bump golang from 869193e to 3bd4475

Bumps golang from `869193e` to `3bd4475`.

---
updated-dependencies:
- dependency-name: golang
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.21.6-alpine3.18@sha256:869193e7c30611d635c7bc3d1ed879039b7d24710a03474437d402f06825171e AS build
+FROM golang:1.21.6-alpine3.18@sha256:3bd447580bc0df66bada3d8e38f37ca85faf66d6a0e37f0ccba287eaf5962757 AS build
 
 COPY . /go/src/github.com/jauderho/bl3auto
 WORKDIR /go/src/github.com/jauderho/bl3auto