Release 2025-07-21 did not build on cmti

[niklassiemer]

The https://github.com/pyiron/docker-stacks/releases/tag/2025-07-21 release failed while building on the cluster with the following mamba error:

Solving environment: ...working... failed

LibMambaUnsatisfiableError: Encountered problems while solving:
  - nothing provides __glibc >=2.34 needed by sysroot_linux-64-2.34-h087de78_2

Could not solve for environment specs
The following package could not be installed
└─ sysroot_linux-64 ==2.34 h087de78_2 is not installable because it requires
   └─ __glibc >=2.34 , which is missing on the system.

[niklassiemer]

Fixed with #591