add gettext to prepare_install()

[mrjones-plip]

This PR adds gettext to the list of apps to check for in prepare_install() and install if they're missing.

I was running the quick start call on a minimal Ubuntu 24.04 server:

curl -sSL https://github.com/jumpserver/jumpserver/releases/latest/download/quick_start.sh | bash

However, I got an error during install gettext: command not found (see full context below). Running apt install gettext fixed the issue

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Processing triggers for libc-bin (2.39-0ubuntu8.4) ...
download install script to /opt/jumpserver-installer-v4.10.1


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                                                                   Version:  v4.10.1-ce  

/opt/jumpserver-installer-v4.10.1/scripts/utils.sh: line 461: gettext: command not found
1. 
/opt/jumpserver-installer-v4.10.1/scripts/utils.sh: line 462: gettext: command not found
: /opt/jumpserver/config
/opt/jumpserver/config/config.txt        [ √ ]
/opt/jumpserver/config/loki/promtail.yml         [ √ ]
/opt/jumpserver/config/nginx/cert/server.crt     [ √ ]
/opt/jumpserver/config/nginx/cert/server.key     [ √ ]
/opt/jumpserver-installer-v4.10.1/scripts/4_install_jumpserver.sh: line 88: gettext: command not found

>>> 
/opt/jumpserver-installer-v4.10.1/scripts/2_install_docker.sh: line 189: gettext: command not found
1. 
/opt/jumpserver-installer-v4.10.1/scripts/utils.sh: line 429: gettext: command not found
gettext:  gettext

./jmsctl.sh: line 81: docker: command not found
root@jumpserver-test:~# gettext