update workflows to pin python-3.12 when installing conda-build

[vtavana]

conda-build is not available for python-3.13. In this PR, python-3.12 is pinned to be used when installing conda-build.

LibMambaUnsatisfiableError: Encountered problems while solving:
  - package conda-build-3.0.22-py27h62b9468_0 requires python >=2.7,<2.8.0a0, but none of the providers can be installed

Could not solve for environment specs
The following packages are incompatible
├─ conda-build =* * is installable with the potential options
│  ├─ conda-build [24.1.0|24.1.1|...|3.28.4] would require
│  │  └─ python >=3.10,<3.11.0a0 *, which can be installed;
│  ├─ conda-build [24.1.0|24.1.1|...|3.28.4] would require
│  │  └─ python >=3.11,<3.12.0a0 *, which can be installed;
│  ├─ conda-build [24.1.0|24.1.1|...|25.4.2] would require
│  │  └─ python >=3.12,<3.13.0a0 *, which can be installed;
│  ├─ conda-build [24.1.0|24.1.1|...|3.28.4] would require
│  │  └─ python >=3.8,<3.9.0a0 *, which can be installed;
│  ├─ conda-build [24.1.0|24.1.1|...|3.28.4] would require
│  │  └─ python >=3.9,<3.10.0a0 *, which can be installed;
│  ├─ conda-build [3.0.[22]|3.0.23|...|3.9.2] would require
│  │  └─ python >=2.7,<2.8.0a0 *, which can be installed;
│  ├─ conda-build [3.0.22|3.0.[23]|...|3.9.2] would require
│  │  └─ python >=3.5,<3.6.0a0 *, which can be installed;
│  ├─ conda-build [3.0.22|3.0.23|...|3.9.2] would require
│  │  └─ python >=3.6,<3.7.0a0 *, which can be installed;
│  └─ conda-build [3.10.9|3.11.0|...|3.23.3] would require
│     └─ python >=3.7,<3.8.0a0 *, which can be installed;
└─ pin on python 3.13.* =* * is not installable because it requires
   └─ python =3.13 *, which conflicts with any installable versions previously reported.

Pins seem to be involved in the conflict. Currently pinned specs:
 - python=3.13