fix: update kit Xcode projects to use main branch

[thomson-t]

Summary

• Updated 6 kit project.pbxproj files that still referenced workstation/9.0-Release branch to use main
• Affected kits: Firebase (firebase-11, firebase-12), FirebaseGA4 (firebase-ga4-11, firebase-ga4-12), UrbanAirship (urbanairship-19, urbanairship-20)

Testing

• Verified no remaining workstation references in Kits/ directory
• Kit Xcode projects open and resolve the SDK dependency correctly

🤖 Generated with Claude Code

[cursor]

PR Summary

Low Risk
Low risk project-configuration change limited to SwiftPM dependency branch selection; main risk is builds resolving a different SDK revision than the previously pinned release branch.

Overview
Updates six kit Xcode projects (Firebase 11/12, Firebase GA4 11/12, UrbanAirship 19/20) to resolve the mparticle-apple-sdk Swift Package dependency from the main branch instead of the legacy workstation/9.0-Release branch.

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[github-actions]

📦 SDK Size Impact Report

Measures how much the SDK adds to an app's size (with-SDK minus without-SDK).

Metric	Target Branch	This PR	Change
App Bundle Impact	1.75 MB	1.75 MB	+N/A
Executable Impact	848 bytes	848 bytes	+N/A
XCFramework Size	6.38 MB	6.38 MB	+N/A

➡️ SDK size impact change is minimal.

Raw measurements

Target branch (main):

{"baseline_app_size_kb":84,"baseline_executable_size_bytes":75464,"with_sdk_app_size_kb":1880,"with_sdk_executable_size_bytes":76312,"sdk_impact_kb":1796,"sdk_executable_impact_bytes":848,"xcframework_size_kb":6532}

This PR:

{"baseline_app_size_kb":84,"baseline_executable_size_bytes":75464,"with_sdk_app_size_kb":1880,"with_sdk_executable_size_bytes":76312,"sdk_impact_kb":1796,"sdk_executable_impact_bytes":848,"xcframework_size_kb":6532}