No boost dependency anymore

[romanc]

Description

Newer GT4Py versions ship with a vendored in version of the boost header file that it needs. And since NDSL updated its GT4Py version, we don't need to install boost anymore in the Dockerfile for PyFV3. Not sure if anyone uses the docker version, but it's easy enough to just clean up.

For the record: The relevant GT4Py update in NDSL was done in NOAA-GFDL/NDSL#150.

How Has This Been Tested?

By doing a self-review of the code changes.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas: N/A
• I have made corresponding changes to the documentation: N/A
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included: N/A
• Targeted model if this changed was triggered by a model need/shortcoming: N/A

[romanc]

@oelbert I read you were waiting for this happen for a long time. Please take the pleasure in reviewing.

/cc @FlorianDeconinck FYI