limit zarr to under 3 if installed with python-elf

[hmaarrfk]

Merge after: conda-forge/python-elf-feedstock#20

See discussion in: conda-forge/micro_sam-feedstock#29

Checklist

• Used a static YAML file for the patch if possible (instructions).
• Only wrote code directly into generate_patch_json.py if absolutely necessary.
• Ran pre-commit run -a and ensured all files pass the linting checks.
• Ran python show_diff.py and posted the output as part of the PR.
• Modifications won't affect packages built in the future.

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe/meta.yaml) and found it was in an excellent condition.

[hmaarrfk]

$ python show_diff.py --subdirs noarch
================================================================================
================================================================================
noarch
noarch::python-elf-0.3.0post0-pyhd8ed1ab_0.tar.bz2
noarch::python-elf-0.3.1-pyhd8ed1ab_0.tar.bz2
noarch::python-elf-0.4.0-pyhd8ed1ab_0.tar.bz2
noarch::python-elf-0.4.1-pyhd8ed1ab_0.tar.bz2
noarch::python-elf-0.4.2-pyhd8ed1ab_0.tar.bz2
noarch::python-elf-0.4.3-pyhd8ed1ab_0.tar.bz2
noarch::python-elf-0.4.4-pyhd8ed1ab_0.tar.bz2
noarch::python-elf-0.4.5-pyhd8ed1ab_0.tar.bz2
noarch::python-elf-0.4.6-pyhd8ed1ab_0.conda
noarch::python-elf-0.4.7-pyhd8ed1ab_0.conda
noarch::python-elf-0.4.8-pyhd8ed1ab_0.conda
noarch::python-elf-0.5.0-pyhd8ed1ab_0.conda
noarch::python-elf-0.5.0-pyhd8ed1ab_1.conda
noarch::python-elf-0.5.1-pyhd8ed1ab_0.conda
noarch::python-elf-0.5.2-pyhd8ed1ab_0.conda
noarch::python-elf-0.5.2-pyhd8ed1ab_1.conda
noarch::python-elf-0.6.0-pyhd8ed1ab_0.conda
+  "constrains": [
+    "zarr <3.0a0"
+  ],