[Docker] Fixing build failure (#7870)

[loginakhil]

• Copying swagger-generator in Dockerfile to fix docker build failures (Docker build failure #7870)

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
• Filed the PR against the correct branch: 3.0.0 branch for changes related to OpenAPI spec 3.0. Default: master.
• Copied the technical committee to review the pull request if your PR is targeting a particular programming language.

Description of the PR

Docker builds without any errors now

[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/swagger-api/swagger-codegen/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/swagger-api/swagger-codegen/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[loginakhil]

@wing328 Thanks for the update, i have modified the commit to tag my username correctly, please verify.

[whoan]

I would love to see this merged. Thanks @loginakhil .