build(deps): Pin to versioned tag rather than automated

[cpswan]

The present :automated tag isn't very informative about what version of Dart we're getting

- What I did

Changed tag to the present release version 3.2.5

- How to verify it

SHAs are the same:

$ sudo docker buildx imagetools inspect atsigncompany/buildimage:automated --format "{{json .Manifest}}" | jq -r .digest
sha256:df2ef31dba19fa48cffe53cb2d2215148db917737e2e511a3f7f3a59ef0244fe

$ sudo docker buildx imagetools inspect atsigncompany/buildimage:3.2.5 --format "{{json .Manifest}}" | jq -r .digest
sha256:df2ef31dba19fa48cffe53cb2d2215148db917737e2e511a3f7f3a59ef0244fe

- Description for the changelog

build(deps): Pin to versioned tag rather than automated