Revert recent Bullseye Dockerfile changes

Description

Reverts the recent Dockerfile changes for the Bullseye build to get builds working again.

API Changes and Justification

Backwards Compatible Changes

• This change does not modify any class/function/struct/type definitions in a public C header file or any Python class/function definitions
• This change adds new classes/functions/structs/types to a public C header file or Python module

Backwards Incompatible Changes

• This change modifies an existing class/function/struct/type definition in a public C header file or Python module
• This change removes an existing class/function/struct/type from a public C header file or Python module

If any of the Backwards Incompatible check boxes are ticked please provide a justification why this change is necessary and why it needs to be done in a backwards incompatible way.

Review Status

Please provide details on any reviews related to this change and and the associated reviewers.

.gitlab-ci-bullseye.Dockerfile

@@ -4,8 +4,6 @@ LABEL name="LALSuite Nightly - Debian Bullseye" \
       maintainer="Adam Mercer <adam.mercer@ligo.org>" \
       support="Not Supported"
 
-SHELL ["/bin/bash", "-e", "-c"]
-
 # add debian packages to container
 COPY debs /srv/local-apt-repository
 
@@ -17,6 +15,5 @@ RUN apt-get update && \
       apt-get -y install local-apt-repository && \
       /usr/lib/local-apt-repository/rebuild && \
       apt-get update && \
-      PACKAGES=$(lz4cat -d /var/lib/apt/lists/_var_lib_local-apt-repository_._Packages* | grep "^Package:" | awk '{print $2}') && \
-      xargs -t apt-get -y install <<< ${PACKAGES} && \
+      apt-get upgrade && \
       rm -rf /var/lib/apts/lists/*