Upgrade example projects to Xcode 8.2 (#7771)

This avoids Xcode complaining at us about unused xcconfig files (for the
time being).
diff --git a/examples/flutter_gallery/ios/Runner.xcodeproj/project.pbxproj b/examples/flutter_gallery/ios/Runner.xcodeproj/project.pbxproj
index f37650b..85230c3 100644
--- a/examples/flutter_gallery/ios/Runner.xcodeproj/project.pbxproj
+++ b/examples/flutter_gallery/ios/Runner.xcodeproj/project.pbxproj
@@ -142,7 +142,7 @@
 		97C146E61CF9000F007C117D /* Project object */ = {
 			isa = PBXProject;
 			attributes = {
-				LastUpgradeCheck = 0800;
+				LastUpgradeCheck = 0820;
 				ORGANIZATIONNAME = "The Chromium Authors";
 				TargetAttributes = {
 					97C146ED1CF9000F007C117D = {
diff --git a/examples/hello_services/ios/Runner.xcodeproj/project.pbxproj b/examples/hello_services/ios/Runner.xcodeproj/project.pbxproj
index c21e39a..65874d7 100644
--- a/examples/hello_services/ios/Runner.xcodeproj/project.pbxproj
+++ b/examples/hello_services/ios/Runner.xcodeproj/project.pbxproj
@@ -147,7 +147,7 @@
 		97C146E61CF9000F007C117D /* Project object */ = {
 			isa = PBXProject;
 			attributes = {
-				LastUpgradeCheck = 0800;
+				LastUpgradeCheck = 0820;
 				ORGANIZATIONNAME = "The Chromium Authors";
 				TargetAttributes = {
 					97C146ED1CF9000F007C117D = {
diff --git a/examples/hello_world/ios/Runner.xcodeproj/project.pbxproj b/examples/hello_world/ios/Runner.xcodeproj/project.pbxproj
index 5d8eab7..47ba8e2 100644
--- a/examples/hello_world/ios/Runner.xcodeproj/project.pbxproj
+++ b/examples/hello_world/ios/Runner.xcodeproj/project.pbxproj
@@ -142,7 +142,7 @@
 		97C146E61CF9000F007C117D /* Project object */ = {
 			isa = PBXProject;
 			attributes = {
-				LastUpgradeCheck = 0800;
+				LastUpgradeCheck = 0820;
 				ORGANIZATIONNAME = "The Chromium Authors";
 				TargetAttributes = {
 					97C146ED1CF9000F007C117D = {
diff --git a/examples/stocks/ios/Runner.xcodeproj/project.pbxproj b/examples/stocks/ios/Runner.xcodeproj/project.pbxproj
index 76a41aa..fb11db4 100644
--- a/examples/stocks/ios/Runner.xcodeproj/project.pbxproj
+++ b/examples/stocks/ios/Runner.xcodeproj/project.pbxproj
@@ -142,7 +142,7 @@
 		97C146E61CF9000F007C117D /* Project object */ = {
 			isa = PBXProject;
 			attributes = {
-				LastUpgradeCheck = 0800;
+				LastUpgradeCheck = 0820;
 				ORGANIZATIONNAME = "The Chromium Authors";
 				TargetAttributes = {
 					97C146ED1CF9000F007C117D = {