Fix broken link to cli tools in ReadMe.md

[tbkr]

Description

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

🌈🌦️📖🚧 Documentation FDB 🚧📖🌦️🌈
https://sites.ecmwf.int/docs/fdb/pull-requests/PR-287

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.05%. Comparing base (9319a5c) to head (c031265).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #287      +/-   ##
===========================================
- Coverage    71.15%   71.05%   -0.11%     
===========================================
  Files          370      370              
  Lines        23455    23455              
  Branches      2463     2463              
===========================================
- Hits         16690    16666      -24     
- Misses        6765     6789      +24     

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