fix export/import of otherModules property

[ruddell]

Exporting Application JDL containing otherModules (for example when a blueprint is used) results in a JDL with otherModules [[object Object]] which fails when attempting to import.

This PR aligns the logic related to the otherModules property with the blueprints property, which has the same format. With this change, apps generated with blueprints can export valid JDL.

I am not an expert with JDL parsing so any review is appreciated.

To reproduce (also happens with beta v7):

# setup
mkdir reproduction && cd reproduction
npm i generator-jhipster@6.10.5 generator-jhipster-quarkus@1.0.0
jhipster jdl --inline "application{ config{ blueprints [generator-jhipster-quarkus]} }" --skip-install

# export-jdl
# npm link generator-jhipster # if you want to use the main branch
jhipster export-jdl
cat jhipster.jdl | grep object

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[MathieuAA]

Thanks @ruddell :)