fix: use chainguard/git base image for releases

The goreleaser kos: section had golang:1.25 (808MB) as base image,
while .ko.yaml correctly uses cgr.dev/chainguard/git (76MB).
Goreleaser ignores .ko.yaml so the base must be set in both places.

golang:1.25 is a full Go SDK image with hundreds of unnecessary
packages, resulting in a large attack surface and many CVEs in
security scans (visible on Artifact Hub).

cgr.dev/chainguard/git is a minimal image with only git and its
dependencies, patched and maintained by Chainguard.

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Vincent Demeester <vdemeest@redhat.com>

Author: vdemeester

image/git-init/.goreleaser.yml

@@ -29,7 +29,7 @@ kos:
   - id: git-init-image
     build: binary
     main: .
-    base_image: golang:1.25
+    base_image: cgr.dev/chainguard/git
     platforms:
       - all
     tags: