Change POM scope for firebase-appindexing

[agerstner-branch]

Change POM scope for firebase-appindexing from "runtime" to "compile"

Reference

SDK-1606 -- [Android] Change scope of firebase-appindexing to 'compile']

Description

POM scope for firebase-appindexing (optional dependency) was being set to "runtime". This change outputs the scope as "compile" in the POM file.

Testing Instructions

1. Publish (locally) as is ./gradlew publishToMavenLocal
2. Verify POM value of runtime
3. Publish (locally) with change ./gradlew publishToMavenLocal
4. Verify POM value of compile

Risk Assessment [LOW]

• [x] I, the PR creator, have tested — integration, unit, or otherwise — this code.

Reviewer Checklist (To be checked off by the reviewer only)

• [ ] JIRA Ticket is referenced in PR title.
• Correctness & Style
  • [ ] Conforms to AOSP Style Guides
  • [ ] Mission critical pieces are documented in code and out of code as needed.
• [ ] Unit Tests reviewed and test issue sufficiently.
• [ ] Functionality was reviewed in QA independently by another engineer on the team.