[shared_preferences] Update AGP to 8.9.1 (#9106)

replacement for #8957

Changelog not required #9062 as an example. 

## Pre-Review Checklist

Author: reidbaker

packages/shared_preferences/shared_preferences_android/example/android/app/build.gradle

@@ -6,7 +6,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:8.5.1'
+        classpath 'com.android.tools.build:gradle:8.9.1'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }

packages/shared_preferences/shared_preferences_android/example/android/gradle/wrapper/gradle-wrapper.properties

@@ -2,4 +2,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.11.1-all.zip

packages/shared_preferences/shared_preferences_android/example/android/settings.gradle

@@ -19,7 +19,7 @@ pluginManagement {
 // See https://github.com/flutter/flutter/blob/master/docs/ecosystem/Plugins-and-Packages-repository-structure.md#gradle-structure for more info.
 plugins {
   id "dev.flutter.flutter-plugin-loader" version "1.0.0"
-  id "com.android.application" version "8.5.2" apply false
+  id "com.android.application" version '8.9.1' apply false
   id "org.jetbrains.kotlin.android" version "1.9.0" apply false
   id "com.google.cloud.artifactregistry.gradle-plugin" version "2.2.1"
 }