Remove featuretools_sql from docs requirements

[thehomebrewnerd]

Remove featuretools_sql from docs requirements

featuretools_sql was listed as a docs requirement in pyproject.toml, but there is no code executed during the docs build that actually requires featuretools_sql to be installed. Having this as a requirement means that users needed to have Postgres installed before running make installdeps, otherwise the installation of psycopg2 would fail. This PR removes this requirement so that users can run make installdeps without having Postgres installed.

[codecov]

Codecov Report

Merging #2302 (e0094fd) into main (8abf923) will increase coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2302      +/-   ##
==========================================
+ Coverage   99.31%   99.37%   +0.06%     
==========================================
  Files         148      145       -3     
  Lines       17706    17661      -45     
==========================================
- Hits        17584    17551      -33     
+ Misses        122      110      -12     

Impacted Files	Coverage Δ
featuretools/synthesis/__init__.py
featuretools/selection/__init__.py
featuretools/__init__.py

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