Insecure serialization leading to RCE in serialize-javascript
Remove transitive dependency serialize-javascript@^1.7.0, inherited from uglifyjs-webpack-plugin@2.2.0 (already deprecated)
Remove uglifyjs-webpack-plugin and add the new plugin (terser-webpack-plugin)

[Reference any related issues, if applicable.]

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Checklist

[x] PR is assigned to a project: Challenge_gov Board
[x] PR is assigned to a milestone: current sprint
[x] GH issues are assigned to the PR (under Development section on the right hand side)
[x] PR is assigned a reviewer, and requires code review and approval by a teammate
[x] New functionality is tested and all tests are green
[x] I have added unit tests for new functionality or updated existing tests for changes.
[x] I have updated the documentation/README accordingly, if necessary.
[x] If you have DB migration, it is a "safe" migration and you've confirmed it can be rolled back.
[x] If applicable, Controllers modified contain appropriate authorization plugs
[x] This PR has been reviewed by at least one other team member.

GSA / Challenge_gov