Updated apptainer to support version 1.2.5

[potter-s]

Updated to 1.2.5, the last release of 1.2. There may be issues with versions 1.3. I could not get this to work out of the box without tweaks, e.g. by running with --unsquash.

[spackbot-app]

Hi @potter-s! I noticed that the following package(s) don't yet have maintainers:

• apptainer

Are you interested in adopting any of these package(s)? If so, simply add the following to the package class:

    maintainers("potter-s")

If not, could you contact the developers of this package and see if they are interested? You can quickly see who has worked on a package with spack blame:

$ spack blame apptainer

Thank you for your help! Please don't add maintainers without their consent.

You don't have to be a Spack expert or package developer in order to be a "maintainer," it just gives us a list of users willing to review PRs or debug issues relating to this package. A package can have multiple maintainers; just add a list of GitHub handles of anyone who wants to volunteer.

[tldahlgren]

Confirmed the sha256.