NodeJS version change

[DunkieGaming]

Problem

• Uptime Karma fails to install with NodeJS 20 because of a memory leak error

Solution

• Changed nodejs_version=20 to nodejs_version=18 in scripts/_common.sh

PR Status

• [x] Code finished and ready to be reviewed/tested
• [x] The fix/enhancement were manually tested (if applicable)

Automatic tests

Automatic tests can be triggered on https://ci-apps-dev.yunohost.org/ after creating the PR, by commenting "!testme", "!gogogadgetoci" or "By the power of systemd, I invoke The Great App CI to test this Pull Request!". (N.B. : for this to work you need to be a member of the Yunohost-Apps organization)

[orhtej2]

Test update from previous version, if the upgrade script does not fully replace node_modules the app will likely fail to start.

[ketsapiwiq]

!testme

[yunohost-bot]

:carousel_horse:

[ketsapiwiq]

Mmmh but I don't understand the root of this memory leak issue, it does work fine on other people's install. I don't see why it shouldn't be merged tho, provided the upgrade to this node v18 version does indeed work.