FLEX-6241 remove flex-plugins-scripts dependency

[shwet2407]

Contributing to Twilio

FLEX-6241 remove flex-plugins-scripts dependency

All third-party contributors acknowledge that any contributions they provide will be made under the same open-source license that the open-source project is provided under.

• I acknowledge that all my contributions will be made under the project's license.

[codecov]

Codecov Report

❌ Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.56%. Comparing base (65a3b1b) to head (19bcb89).

Files with missing lines	Patch %	Lines
...s/flex-dev-utils/src/errors/lib/FlexPluginError.ts	0.00%	1 Missing ⚠️
.../flex-plugin-webpack/src/webpack/webpack.config.ts	0.00%	1 Missing ⚠️
...n-flex/src/commands/flex/plugins/upgrade-plugin.ts	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1151      +/-   ##
==========================================
- Coverage   89.69%   89.56%   -0.13%     
==========================================
  Files         146      146              
  Lines       14482    14463      -19     
  Branches      983      978       -5     
==========================================
- Hits        12989    12953      -36     
- Misses       1472     1490      +18     
+ Partials       21       20       -1     

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