pre-commit.Dockerfile: add all files in a single COPY (#5562)

also removed comment as it is no longer relevant

Signed-off-by: Filip Kobierski <fkobi@fsfe.org>

I recommend side-by-side diff for reviewing the changes

Reviewed-on: #5562
Reviewed-by: delliott <delliott@fsfe.org>
Co-authored-by: Filip Kobierski <fkobi@fsfe.org>
Co-committed-by: Filip Kobierski <fkobi@fsfe.org>

pre-commit.Dockerfile

@@ -34,13 +34,10 @@ ENV PATH="$UV_PROJECT_ENVIRONMENT/bin:$PATH"
 # Set the workdir
 WORKDIR /website-source-during-build
 
-# Copy the pyproject and build deps
-# Done in a seperate step for optimal docker caching
-COPY ./pyproject.toml ./uv.lock ./
-RUN uv sync --no-install-package fsfe_website_build --group dev
+# Copy pyproject, build deps & entrypoint
+COPY ./pyproject.toml ./uv.lock pre-commit.entrypoint.sh ./
 
-# Copy entrypoint
-COPY pre-commit.entrypoint.sh ./
+RUN uv sync --no-install-package fsfe_website_build --group dev
 
 # Set the workdir
 WORKDIR /website-source