docs: remove -f option in CONTRIBUTING.md

[tttol]

Fixes #

In CONTRIBUTING.md, the command for running integration tests does not work:

$ bin/run-suite -s ../../../../aws-cdk-cli cli-integ-tests -f 2.179.0-t 'cli-lib deploy'
Error: Cannot use --framework-version with --use-source
    at main (/Users/t-takahashi/Documents/workspace/aws-cdk-cli-testing/packages/@aws-cdk-testing/cli-integ/lib/cli/run-suite.js:85:19)

The -f option cannot be used with -s, so I removed -f from the snippet.

---

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.73%. Comparing base (48244a9) to head (6b7319a).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #180      +/-   ##
==========================================
- Coverage   84.75%   84.73%   -0.03%     
==========================================
  Files         205      205              
  Lines       35648    35648              
  Branches     4604     4606       +2     
==========================================
- Hits        30215    30207       -8     
+ Misses       5286     5285       -1     
- Partials      147      156       +9     

Flag	Coverage Δ
suite.unit	84.73% <ø> (-0.03%)	⬇️

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