Update excerpts

Author: aednlaxer

packages/google_maps_flutter/google_maps_flutter/README.md

@@ -128,14 +128,12 @@ in an unbounded widget will cause the application to throw a Flutter exception.
 
 <?code-excerpt "readme_sample_advanced_markers.dart (AdvancedMarkersSample)"?>
 ```dart
-GoogleMap(
+body: GoogleMap(
   // Set your Map Id
   mapId: 'my-map-id',
-  
+
   // Let map know that you're using Advanced Markers
   markerType: MarkerType.advancedMarker,
-  initialCameraPosition: _kGooglePlex,
-),
 ```
 
 ### Sample Usage

packages/google_maps_flutter/google_maps_flutter/example/lib/readme_sample_advanced_markers.dart

@@ -22,7 +22,6 @@ class MyApp extends StatelessWidget {
   }
 }
 
-// #docregion AdvancedMarkersSample
 class AdvancedMarkersSample extends StatelessWidget {
   const AdvancedMarkersSample({super.key});
 
@@ -34,15 +33,16 @@ class AdvancedMarkersSample extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return const Scaffold(
+// #docregion AdvancedMarkersSample
       body: GoogleMap(
         // Set your Map Id
         mapId: 'my-map-id',
 
         // Let map know that you're using Advanced Markers
         markerType: MarkerType.advancedMarker,
+// #enddocregion AdvancedMarkersSample
         initialCameraPosition: _kGooglePlex,
       ),
     );
   }
 }
-// #enddocregion AdvancedMarkersSample