Flutter demos: update Android plugin for 16 KB page size compatibility

Only doing minor changes. Will fully update the examples at some later
point.

Author: greenrobot-team

objectbox/example/flutter/objectbox_demo/android/gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-all.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

objectbox/example/flutter/objectbox_demo/android/settings.gradle

@@ -23,7 +23,7 @@ pluginManagement {
 
 plugins {
     id "dev.flutter.flutter-plugin-loader" version "1.0.0"
-    id "com.android.application" version "8.2.1" apply false // 7.3.0 -> 8.2.1 to support JDK 21
+    id "com.android.application" version "8.5.1" apply false // 8.5.1 to support 16 KB page sizes
 }
 
 include ":app"

objectbox/example/flutter/objectbox_demo_relations/android/gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-all.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

objectbox/example/flutter/objectbox_demo_relations/android/settings.gradle

@@ -23,7 +23,7 @@ pluginManagement {
 
 plugins {
     id "dev.flutter.flutter-plugin-loader" version "1.0.0"
-    id "com.android.application" version "8.2.1" apply false // 7.3.0 -> 8.2.1 to support JDK 21
+    id "com.android.application" version "8.5.1" apply false // 8.5.1 to support 16 KB page sizes
 }
 
 include ":app"

objectbox/example/flutter/objectbox_demo_sync/android/gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-all.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

objectbox/example/flutter/objectbox_demo_sync/android/settings.gradle

@@ -23,7 +23,7 @@ pluginManagement {
 
 plugins {
     id "dev.flutter.flutter-plugin-loader" version "1.0.0"
-    id "com.android.application" version "8.2.1" apply false // 7.3.0 -> 8.2.1 to support JDK 21
+    id "com.android.application" version "8.5.1" apply false // 8.5.1 to support 16 KB page sizes
 }
 
 include ":app"