Fix shifu docs

[BtXin]

What this PR does / why we need it:
We updated shifu doc's link but didn't sync on readme
Will this PR make the community happier?

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

Release note:

[codecov]

Codecov Report

Merging #243 (0c34cf4) into main (1a45ca7) will decrease coverage by 0.08%.
The diff coverage is n/a.

❗ Current head 0c34cf4 differs from pull request most recent head 3cbc854. Consider uploading reports for the commit 3cbc854 to get more accurate results

@@            Coverage Diff             @@
##             main     #243      +/-   ##
==========================================
- Coverage   22.11%   22.03%   -0.09%     
==========================================
  Files           8        8              
  Lines         823      826       +3     
==========================================
  Hits          182      182              
- Misses        624      627       +3     
  Partials       17       17              

Impacted Files	Coverage Δ
pkg/deviceshifu/deviceshifuMQTT/deviceshifuMQTT.go	26.02% <0.00%> (-0.18%)	⬇️
pkg/deviceshifu/deviceshifuHTTP/deviceshifuHTTP.go	15.64% <0.00%> (-0.13%)	⬇️
...deviceshifu/deviceshifuSocket/deviceshifuSocket.go	28.05% <0.00%> (ø)

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