Fix uvh5 reader to check for phase_center_catalog not multi_phase_center

[bhazelton]

Description

Fixes a mismatch between the reader and the documentation where the reader was looking for a boolean (multi_phase_center) to indicate that the phase_center_catalog was present rather than just looking for that
header item.

Motivation and Context

fixes #1224

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation change (documentation changes only)
• Version change
• Build or continuous integration change

Checklist:

• I have read the contribution guide.
• My code follows the code style of this project.

Bug fix checklist:

• My fix includes a new test that breaks as a result of the bug (if possible).
• All new and existing tests pass.
• I have updated the CHANGELOG.

[codecov]

Codecov Report

Merging #1225 (c9f40a1) into main (e76516a) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1225      +/-   ##
==========================================
- Coverage   99.93%   99.93%   -0.01%     
==========================================
  Files          33       33              
  Lines       18065    18062       -3     
==========================================
- Hits        18054    18051       -3     
  Misses         11       11              

Impacted Files	Coverage Δ
pyuvdata/uvdata/uvh5.py	100.00% <100.00%> (ø)

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[bhazelton]

The codecov failure is just because I removed code so the denominator of the percent coverage went down, so not really a concern.

[plaplant]

Looks great, thanks @bhazelton!