refactor(clippy): apply clippy's lint

[ognis1205]

Description

Fixes Clippy lint warnings that caused the CI lint job to fail.

Motivation and Context

The CI lint job was failing on the Lints step.

• example

This change resolves those errors so that the continuous integration pipeline passes successfully and future warnings are caught early.

How Has This Been Tested?

• Ran cargo clippy --tests --verbose -- -D warnings locally and confirmed it exits cleanly with no errors or warnings.
• Ran cargo +nightly fmt --all to ensure formatting is consistent.
• Ran cargo test to verify that all existing tests still pass after the lint fixes.

Screenshots / Logs (if applicable)

N/A

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (no code change)
• Refactor (refactoring production code)
• Other

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly (if applicable).
• I have formatted the code with rustfmt.
  • cargo +nightly fmt --all
• I checked the lints with clippy.
  • cargo clippy --tests --verbose -- -D warnings
• I have added tests to cover my changes.
• All new and existing tests passed.
  • cargo test

[codecov-commenter]

Codecov Report

❌ Patch coverage is 61.85567% with 37 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.34%. Comparing base (8fc0aef) to head (19913b5).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
git-cliff/src/lib.rs	0.00%	29 Missing ⚠️
git-cliff-core/src/config.rs	16.67%	5 Missing ⚠️
git-cliff-core/src/changelog.rs	90.91%	2 Missing ⚠️
git-cliff-core/src/commit.rs	96.78%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1631      +/-   ##
==========================================
+ Coverage   53.27%   53.34%   +0.08%     
==========================================
  Files          28       28              
  Lines        2621     2625       +4     
==========================================
+ Hits         1396     1400       +4     
  Misses       1225     1225              

Flag	Coverage Δ
unit-tests	53.34% <61.86%> (+0.08%)	⬆️

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