Update application.properties

[stephenbjm]

The underlying enum uses uppercase for WEB_APP instead of lowercase.

Check list:

Your pull request:

• [ ] targets the development branch
• [ ] uses the 999-SNAPSHOT version of Quarkus
• [ ] has tests (mvn clean test)
• [ ] works in native (mvn clean package -Pnative)
• [ ] has integration/native tests (mvn clean verify -Pnative)
• [ ] makes sure the associated guide must not be updated
• [ ] links the guide update pull request (if needed)
• [ ] updates or creates the README.md file (with build and run instructions)
• [ ] for new quickstart, is located in the directory component-quickstart
• [ ] for new quickstart, is added to the root pom.xml and README.md

[gsmet]

Was it actually a problem? Because this is supposed to work, our config layer does the translation.