Update Apptainer cache directory path

[CodingKaiser]

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name: New Config about: A new cluster config

Please follow these steps before submitting your PR:

• [ ] If your PR is a work in progress, include [WIP] in its title
• [ ] Your PR targets the master branch
• [ ] You've included links to relevant issues, if any

Steps for adding a new config profile:

• [ ] Add your custom config file to the conf/ directory
• [ ] Add your documentation file to the docs/ directory
• [ ] Add your custom profile to the nfcore_custom.config file in the top-level directory
• [ ] Add your profile name to the profile: scope in .github/workflows/main.yml
• [ ] OPTIONAL: Add your custom profile path and GitHub user name to .github/CODEOWNERS (**/<custom-profile>** @<github-username>)

[pontus]

If you haven't received it before, here's your "mandatory" warning that having a system wide image cachedir is generally not a good idea for larger clusters (basically, it makes anyone running nf-core pipelines with that profile fully trust everyone else on the system enough to run their code as themselves).

Using a libraryDir that's managed by a trusted set of users is generally a much better idea.