Enable SPM support only for iOS15+

Author: jokerttu

packages/google_maps_flutter/google_maps_flutter_ios/README.md

@@ -21,5 +21,10 @@ should add it to your `pubspec.yaml` as usual.
 | Heatmap.maximumZoomIntensity |     ✓     |
 | HeatmapGradient.colorMapSize |     ✓     |
 
+## Swift Package Manager Support
+
+This package supports Swift Package Manager for projects targeting iOS 15 or above. For projects targeting iOS 14, you need to disable Swift Package Manager. For more information on how to disable Swift Package Manager for a single project, refer to [this document][3].
+
 [1]: https://pub.dev/packages/google_maps_flutter
 [2]: https://flutter.dev/to/endorsed-federated-plugin
+[3]: https://docs.flutter.dev/packages-and-plugins/swift-package-manager/for-app-developers#turn-off-for-a-single-project

packages/google_maps_flutter/google_maps_flutter_ios/example/ios14/pubspec.yaml

@@ -29,6 +29,9 @@ dev_dependencies:
     sdk: flutter
 
 flutter:
+  # Swift Package Manager for google_maps_flutter_ios does not support iOS 14,
+  # so it needs to be disabled for this example project.
+  disable-swift-package-manager: true
   uses-material-design: true
   assets:
     - assets/

packages/google_maps_flutter/google_maps_flutter_ios/ios/google_maps_flutter_ios/Package.swift

@@ -10,14 +10,14 @@ import PackageDescription
 let package = Package(
     name: "google_maps_flutter_ios",
     platforms: [
-        .iOS(.v14),
+        .iOS(.v15),
     ],
     products: [
         .library(name: "google-maps-flutter-ios", type: .static, targets: ["google_maps_flutter_ios"])
     ],
     dependencies: [
-        .package(url: "https://github.com/googlemaps/ios-maps-sdk", "8.4.0"..<"10.0.0"),
-        .package(url: "https://github.com/googlemaps/google-maps-ios-utils", "5.0.0"..<"7.0.0"),
+        .package(url: "https://github.com/googlemaps/ios-maps-sdk", "9.0.0"..<"10.0.0"),
+        .package(url: "https://github.com/googlemaps/google-maps-ios-utils", "6.1.0"..<"7.0.0"),
     ],
     targets: [
         .target(