fix link to settings section in README.rst

[owocado]

Hi,

I observed that in README, current URL for settings section of the docs leads to usage section, so this PR fixes the URL to properly redirect the readers to correct settings section of dateparser docs.

P.S. thank you for creating dateparser! ❤️

[lopuhin]

Looks great, thanks for the catch @ow0x

[lopuhin]

let me just make sure tests pass

[codecov]

Codecov Report

Merging #1018 (4c905f2) into master (5ec1a6e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1018   +/-   ##
=======================================
  Coverage   98.29%   98.29%           
=======================================
  Files         234      234           
  Lines        2694     2694           
=======================================
  Hits         2648     2648           
  Misses         46       46           

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