docs: remove duplicated file name

[yajo]

Description

.cz.toml is specified twice and gets confusing.

Checklist

• Add test cases to all the changes you introduce
• Run ./script/format and ./script/test locally to ensure this change passes linter check and test
• Test the changes on the local machine manually
• Update the documentation for the changes

[codecov]

Codecov Report

Merging #363 (8902b40) into master (ed06664) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #363      +/-   ##
==========================================
+ Coverage   97.53%   97.56%   +0.02%     
==========================================
  Files          39       39              
  Lines        1340     1356      +16     
==========================================
+ Hits         1307     1323      +16     
  Misses         33       33              

Flag	Coverage Δ
unittests	97.56% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
commitizen/cli.py	97.50% <ø> (ø)
commitizen/__version__.py	100.00% <100.00%> (ø)
commitizen/commands/bump.py	95.19% <100.00%> (+0.74%)	⬆️
commitizen/out.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e8955d4...8902b40. Read the comment docs.