Fix get team members (resolves #23)

[dignissimus]

Previously the API returned a 404 error since the URL was incorrect, the correct url is given by the Lichess API documentation. (https://lichess.org/api#operation/teamIdUsers)

Resolves #23

[codecov-io]

Codecov Report

Merging #29 (c62c1bb) into master (1b000a4) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master      #29   +/-   ##
=======================================
  Coverage   70.04%   70.04%           
=======================================
  Files           8        8           
  Lines         671      671           
=======================================
  Hits          470      470           
  Misses        201      201           

Impacted Files	Coverage Δ
berserk/clients.py	33.70% <0.00%> (ø)

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