Lock signal-cli at 0.11.11 while maintaining native mode

[mattwr18]

Motive:

We actually inadvertently changed the mode of signal-cli from normal mode to native mode in fix(signal-cli-rest-api): native mode #1687. This, in combination with upgrading signal-cli-rest-api to 0.68, which upgrades signal-cli to 0.12.1 and libsignal to 0.30.0 breaks the implementation of Signal.

We could simply change back to using normal mode, which we have done since we introduced Signal, but we could benefit from native mode since it is much faster and uses less memory. We have periodically dealt with issues related to lack of RAM and have subsequently upgraded all our droplets, since they all use Signal. See https://tactilenews.slack.com/archives/C010QDQLCKW/p1670574356400719

The idea is to lock the signal-cli version to 0.11.11 and still make use of recent changes to error handling, introduced by @roschaefer in fix: include $stdin in server response on error #404. We will then monitor the status of the issue with upgrading and decide either to upgrade after the issue is resolved upstream, or go back to normal mode.

[mattwr18]

Closing as we now upgraded to >0.12.2 in #1714