Docker: remove redundant dos2unix calls (#28839)

I'm assuming these were here because, at some point, someone checked in some
files with CRLF line endings. However, they are no longer there, installing
dos2unix slows down the build, and just don't do that, m'kay?

Dockerfile

@@ -6,15 +6,12 @@ ARG USE_CUSTOM_SDKS=false
 ARG JS_SDK_REPO="https://github.com/matrix-org/matrix-js-sdk.git"
 ARG JS_SDK_BRANCH="master"
 
-RUN apt-get update && apt-get install -y git dos2unix
-
 WORKDIR /src
 
 COPY . /src
-RUN dos2unix /src/scripts/docker-link-repos.sh && bash /src/scripts/docker-link-repos.sh
+RUN /src/scripts/docker-link-repos.sh
 RUN yarn --network-timeout=200000 install
-
-RUN dos2unix /src/scripts/docker-package.sh /src/scripts/get-version-from-git.sh /src/scripts/normalize-version.sh && bash /src/scripts/docker-package.sh
+RUN /src/scripts/docker-package.sh
 
 # Copy the config now so that we don't create another layer in the app image
 RUN cp /src/config.sample.json /src/webapp/config.json