chore(mobile): drop support for iOS 14 (#29780)

chore(mobile): drop support for iOS 14 in advance of iOS and Xcode 27

mobile/ios/Podfile

@@ -1,5 +1,5 @@
 # Uncomment this line to define a global platform for your project
-platform :ios, '14.0'
+platform :ios, '15.0'
 
 # CocoaPods analytics sends network stats synchronously affecting flutter build latency.
 ENV['COCOAPODS_DISABLE_STATS'] = 'true'
@@ -45,7 +45,7 @@ post_install do |installer|
   installer.generated_projects.each do |project|
     project.targets.each do |target|
         target.build_configurations.each do |config|
-            config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = '14.0'
+            config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = '15.0'
         end
     end
   end