Fix Redshift query for external tables

[woop]

Signed-off-by: Willem Pienaar git@willem.co

What this PR does / why we need it:

Currently it's not possible to use ANY_VALUE with Redshift Spectrum (when querying features on S3). This PR changes ANY_VALUE to MAX

Does this PR introduce a user-facing change?:

Fixed a bug in Redshift training dataset generation where queries failed on external tables

[codecov-commenter]

Codecov Report

Merging #1810 (fb316e4) into master (998e169) will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1810      +/-   ##
==========================================
- Coverage   84.85%   84.81%   -0.05%     
==========================================
  Files          92       92              
  Lines        6828     6828              
==========================================
- Hits         5794     5791       -3     
- Misses       1034     1037       +3     

Flag	Coverage Δ
integrationtests	84.76% <ø> (-0.02%)	⬇️
unittests	63.94% <ø> (ø)

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Impacted Files	Coverage Δ
sdk/python/feast/infra/offline_stores/redshift.py	90.29% <ø> (ø)
sdk/python/feast/infra/online_stores/datastore.py	90.51% <0.00%> (-2.59%)	⬇️

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[achals]

/lgtm

[feast-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: achals, woop

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