docs: update CONTRIBUTING.md

--gpg-sign is used instead -S which makes better understanding

CONTRIBUTING.md

@@ -79,11 +79,11 @@ Before you submit your Pull Request (PR) consider the following guidelines:
   is necessary because release notes are automatically generated from these messages.
 
      ```shell
-     git commit -a -S
+     git commit -a --gpg-sign
      ```
   Note: The optional commit `-a` command line option will automatically "add" and "rm" edited files.
 
-  Note: The command line option `-S` generates a signed commit, which is required to make a contribution (See [Developer Certificate of Origin](./LICENSES/DCO.txt))
+  Note: The command line option `-S/--gpg-sign` generates a signed commit, which is required to make a contribution (See [Developer Certificate of Origin](./LICENSES/DCO.txt))
 
 * Push your branch to GitHub:
 
@@ -104,4 +104,3 @@ To ensure consistency throughout the source code, keep these rules in mind as yo
 * All features or bug fixes **must be tested** by one or more specs (unit-tests).
 * All API methods **must be documented**.
 * Also see [CODING_STANDARDS.md](./CODING_STANDARDS.md)
-

Dockerfile

@@ -1,4 +1,4 @@
 FROM python:3.12.5-slim@sha256:59c7332a4a24373861c4a5f0eec2c92b87e3efeb8ddef011744ef9a751b1d11c
 LABEL maintainer="SBB Polarion Team <[email protected]>"
 
-ARG APP_IMAGE_VERSION=0.0.0-dev
+ARG APP_IMAGE_VERSION=0.0.0-dev