Set Frontier to 56 cores per node.

[joaander]

Description

Set Frontier to 56 cores per node.

Motivation and Context

Frontier makes 56 cores available per node by default and discourages overriding this: https://docs.olcf.ornl.gov/systems/frontier_user_guide.html#low-noise-mode-layout

Checklist:

• I am familiar with the Contributing Guidelines.
• I agree with the terms of the Contributor Agreement.
• My name is on the list of contributors.
• The changes introduced by this pull request are covered by existing or newly introduced tests.
• The package documentation and framework documentation in signac-docs are up to date with these changes.
• I have updated the changelog and added any related issue and pull request numbers for future reference.

[codecov]

Codecov Report

Merging #764 (914dc56) into main (3652e68) will decrease coverage by 0.14%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #764      +/-   ##
==========================================
- Coverage   69.28%   69.14%   -0.14%     
==========================================
  Files          43       43              
  Lines        4294     4294              
  Branches     1047     1047              
==========================================
- Hits         2975     2969       -6     
- Misses       1108     1114       +6     
  Partials      211      211              

Files Changed	Coverage Δ
flow/environments/incite.py	86.36% <100.00%> (ø)

... and 1 file with indirect coverage changes