refactor: use the 'String#endsWith' method instead

[noritaka1166]

What kind of change does this PR introduce?
refactoring

Did you add tests for your changes?
no

If relevant, did you update the documentation?
no

Summary

• Use the 'String#endsWith' method instead

Does this PR introduce a breaking change?
no

Other information
no

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.97%. Comparing base (31f634a) to head (7db3d4b).
Report is 236 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4460      +/-   ##
==========================================
- Coverage   90.18%   89.97%   -0.22%     
==========================================
  Files          22        9      -13     
  Lines        1702     1416     -286     
  Branches      491      469      -22     
==========================================
- Hits         1535     1274     -261     
+ Misses        167      142      -25     

Files with missing lines	Coverage Δ
packages/webpack-cli/src/webpack-cli.ts	91.06% <100.00%> (-1.57%)	⬇️

... and 3 files with indirect coverage changes

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