fix(readme): use new demo server

[numb3r3]

update the readme to use the new service hosted at api.clip.jina.ai

[codecov]

Codecov Report

Merging #819 (f859b9b) into main (fa7e577) will decrease coverage by 10.91%.
The diff coverage is n/a.

❗ Current head f859b9b differs from pull request most recent head 9b14f49. Consider uploading reports for the commit 9b14f49 to get more accurate results

@@             Coverage Diff             @@
##             main     #819       +/-   ##
===========================================
- Coverage   84.30%   73.38%   -10.92%     
===========================================
  Files          21       21               
  Lines        1548     1548               
===========================================
- Hits         1305     1136      -169     
- Misses        243      412      +169     

Flag	Coverage Δ
cas	73.38% <ø> (-10.92%)	⬇️

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Impacted Files	Coverage Δ
server/clip_server/executors/clip_tensorrt.py	0.00% <0.00%> (-92.73%)	⬇️
server/clip_server/model/clip_trt.py	0.00% <0.00%> (-85.72%)	⬇️
server/clip_server/model/trt_utils.py	0.00% <0.00%> (-83.52%)	⬇️

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[jemmyshin]

LGTM