Fix documentation Openfeature server sdk

[thomaspoignant]

Description

OpenFeature has changed package name from js-sdk to server-sdk, updating the documentation.

Checklist

• I have updated the documentation (README.md and /website/docs)
• I have followed the contributing guide

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[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (23ed505) 88.78% compared to head (bbf6344) 88.78%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1339   +/-   ##
=======================================
  Coverage   88.78%   88.78%           
=======================================
  Files          71       71           
  Lines        3316     3316           
=======================================
  Hits         2944     2944           
  Misses        302      302           
  Partials       70       70           

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