Fix nlp_primitives installation and remove extra requirement

[rwedge]

Fix #925

Two issues:

1. The nlp_primitives library is in the core-requirements.txt file twice -- once as featuretools[nlp_primitives], once as nlp-primitives
2. Tensorflow needs an older version of scipy than pip is installing:

This error doesn't appear to be impacting things but can be fixed by adding an upper bound for the scipy package, until tensorflow removes their upper bound.

It might also be a good idea to set minimum requirements for the featuretools / nlp primitives libraries but that may be out of scope

[codecov]

Codecov Report

Merging #924 into main will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #924   +/-   ##
=======================================
  Coverage   99.83%   99.83%           
=======================================
  Files         170      170           
  Lines        8578     8578           
=======================================
  Hits         8564     8564           
  Misses         14       14           

Impacted Files	Coverage Δ
evalml/tests/utils_tests/test_cli_utils.py	100.00% <100.00%> (ø)

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[dsherry]

Thanks @rwedge ! Makes sense to me

[dsherry]

I tried this out locally and it fixed the issue for me. And I didn't see the error/warning I mentioned in #925