Rename application.sass.scss to application.scss

[Nitemaeric]

Context

We don't need the additional .sass extension.

Changes proposed in this pull request

Rename application.sass.scss to application.scss.

Guidance to review

Application CSS should still compile as usual.

Link to Trello card

https://trello.com/c/qSOonuo4/101-rename-applicationsassscss-to-applicationscss

Things to check

• If the code removes any existing feature flags, a data migration has also been added to delete the entry from the database
• This code does not rely on migrations in the same Pull Request
• If this code includes a migration adding or changing columns, it also backfills existing records for consistency
• If this code adds a column to the DB, decide whether it needs to be in analytics yml file or analytics blocklist
• API release notes have been updated if necessary
• If it adds a significant user-facing change, is it documented in the CHANGELOG?
• Required environment variables have been updated or added to the Azure KeyVault

[Nitemaeric]

Rename application.sass.scss to application.scss