[fuchsia] Replace amberctl in serve.sh with pkgctl (#28660)
[fuchsia] Replace amberctl in serve.sh with pkgctl (#28660)

Fixes: fxb/89785
flutter/engine,chinmaygarde/flutter_engine,flutter/engine,rmacnak-google/engine,jason-simmons/flutter_engine,aam/engine,rmacnak-google/engine,chinmaygarde/flutter_engine,Hixie/sky_engine,flutter/engine,rmacnak-google/engine,devoncarew/engine,chinmaygarde/flutter_engine,Hixie/sky_engine,jason-simmons/flutter_engine,aam/engine,flutter/engine,Hixie/sky_engine,Hixie/sky_engine,jason-simmons/flutter_engine,rmacnak-google/engine,devoncarew/engine,devoncarew/engine,Hixie/sky_engine,flutter/engine,jason-simmons/flutter_engine,aam/engine,rmacnak-google/engine,Hixie/sky_engine,aam/engine,Hixie/sky_engine,rmacnak-google/engine,jason-simmons/flutter_engine,flutter/engine,chinmaygarde/flutter_engine,chinmaygarde/flutter_engine,devoncarew/engine,chinmaygarde/flutter_engine,devoncarew/engine,flutter/engine,jason-simmons/flutter_engine,chinmaygarde/flutter_engine,rmacnak-google/engine,aam/engine,jason-simmons/flutter_engine,flutter/engine,aam/engine,jason-simmons/flutter_engine,Hixie/sky_engine,aam/engine,devoncarew/engine,devoncarew/engine,aam/engine