Bump to ggshield 1.15.0

Author: agateau-gg

action.yml

@@ -23,7 +23,7 @@ branding:
   color: "blue"
 runs:
   using: "docker"
-  image: "docker://gitguardian/ggshield:v1.14.5"
+  image: "docker://gitguardian/ggshield:v1.15.0"
   entrypoint: "/app/docker/actions-secret-entrypoint.sh"
   args:
     - ${{ inputs.args }}