fix(env): ENG-5157 bundle only one env in release mode

[crherman7]

Describe your changes

In release mode only bundle one env - equality test will look directly at file name rather than regex.

Issue ticket number and link

Ticket

Type of change

• Bug fix (non-breaking change which fixes an issue)

Test Plan

1. yarn install
2. yarn build
3. cd apps/example
4. yarn flagship-code prebuild --env prod --build internal --release
5. go to node_modules/@brandingbrand/fsapp/src/project_env_index.js
6. verify only one env

Checklist before requesting a review

• A self-review of my code has been completed
• Tests have been added / updated if required
• Documentation has been updated to reflect these changes