fix: Remove premature SPM implementation to avoid file duplication

Swift Package Manager support should be implemented properly without
duplicating source files. The current implementation created file duplication
which is not the correct approach.

Need to:
- Research proper Flutter SPM integration without file duplication
- Add CI/CD for testing both CocoaPods and SPM compatibility
- Implement SPM support correctly using symlinks or shared sources

Thanks to @ened for pointing out the duplication issue.

Author: ened

workmanager/CHANGELOG.md

@@ -6,7 +6,7 @@
 * iOS: Add Privacy Manifest for App Store compliance by @navaronbracke (from PR #555)
 * iOS: Replace print statements with proper os_log for better logging
 * iOS: printScheduledTasks now returns String instead of void by @yarith28 (from PR #585)
-* iOS: Add Swift Package Manager support for future Flutter compatibility (Package.swift)
+* iOS: Prepare for Swift Package Manager support (requires proper implementation without file duplication)
 
 # 0.7.0