Bump alpine (#1519)

Bumps the all-deps group in /trillian/examples/deployment/docker/envsubst with 1 update: alpine.


Updates `alpine` from `77726ef` to `b89d9c9`

---
updated-dependencies:
- dependency-name: alpine
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: all-deps
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

trillian/examples/deployment/docker/envsubst/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.20@sha256:77726ef6b57ddf65bb551896826ec38bc3e53f75cdde31354fbffb4f25238ebd
+FROM alpine:3.20@sha256:b89d9c93e9ed3597455c90a0b88a8bbb5cb7188438f70953fede212a0c4394e0
 
 RUN apk add --no-cache gettext