Support pandas v2

[corneliusroemer]

Support pandas v2.

Pathogen CI uses whatever pandas version is installed by conda base if augur doesn't have conflicting requirements, which is v1 right now, so I made an ephemeral test PR to exclude v2 to test pathogen CI with v2 and it passed, see #1672

Related issue(s)

Resolves #1471
Part of nextstrain/public#12

Checklist

• Automated checks pass
• Check if you need to add a changelog message
• Check if you need to add tests
• Check if you need to update docs

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 72.30%. Comparing base (4b5ad2a) to head (5b4efab).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
augur/parse.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    nextstrain/augur#1671      +/-   ##
==========================================
+ Coverage   72.29%   72.30%   +0.01%     
==========================================
  Files          79       79              
  Lines        8276     8276              
  Branches     1691     1691              
==========================================
+ Hits         5983     5984       +1     
+ Misses       2008     2007       -1     
  Partials      285      285              

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[victorlin]

I've moved the post-merge checklist to the task list in nextstrain/public#12

[corneliusroemer]

Not merging this yet so we can release what's on master right now (quite a bit), so we can detect pandas changes in a following release.