[ Docs ] fix: contribute link

[taieeuu]

Why are the changes needed?

Current link is broken.

What changes were proposed in this pull request?

Fix contribute link in README.

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 37.10%. Comparing base (92f8abb) to head (e4e1de9).
Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6076      +/-   ##
==========================================
- Coverage   37.10%   37.10%   -0.01%     
==========================================
  Files        1318     1318              
  Lines      132331   132331              
==========================================
- Hits        49100    49095       -5     
- Misses      78959    78963       +4     
- Partials     4272     4273       +1     

Flag	Coverage Δ
unittests-datacatalog	51.58% <ø> (ø)
unittests-flyteadmin	54.07% <ø> (-0.03%)	⬇️
unittests-flytecopilot	30.99% <ø> (ø)
unittests-flytectl	62.33% <ø> (+0.04%)	⬆️
unittests-flyteidl	7.23% <ø> (ø)
unittests-flyteplugins	53.82% <ø> (ø)
unittests-flytepropeller	42.63% <ø> (ø)
unittests-flytestdlib	57.54% <ø> (-0.06%)	⬇️

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