[image_picker_ios] In unit test write and read kCGImagePropertyExifUserComment property (flutter#3783)

`testSaveImageWithPickerInfo_ShouldSaveWithTheCorrectExtentionAndMetaData`
passed on iOS 16 but not iOS 16.2. For some reason the latter doesn't
want maintain `kCGImagePropertyExifMakerNote`. Swap to
`kCGImagePropertyExifUserComment` which does work on both versions, and
tests the same thing: metadata can be written and read.

Fixes flutter#125257

Author: jmagman

packages/image_picker/image_picker_ios/CHANGELOG.md

@@ -1,3 +1,6 @@
+## NEXT
+* Updates metadata unit test to work on iOS 16.2.
+
 ## 0.8.7+3
 
 * Updates pigeon to fix warnings with clang 15.

packages/image_picker/image_picker_ios/example/ios/RunnerTests/PhotoAssetUtilTests.m

@@ -76,7 +76,7 @@ - (void)testSaveImageWithPickerInfo_ShouldSaveWithTheCorrectExtentionAndMetaData
   NSDictionary *dummyInfo = @{
     UIImagePickerControllerMediaMetadata : @{
       (__bridge NSString *)kCGImagePropertyExifDictionary :
-          @{(__bridge NSString *)kCGImagePropertyExifMakerNote : @"aNote"}
+          @{(__bridge NSString *)kCGImagePropertyExifUserComment : @"aNote"}
     }
   };
   UIImage *imageJPG = [UIImage imageWithData:ImagePickerTestImages.JPGTestData];
@@ -86,7 +86,7 @@ - (void)testSaveImageWithPickerInfo_ShouldSaveWithTheCorrectExtentionAndMetaData
   NSData *data = [NSData dataWithContentsOfFile:savedPathJPG];
   NSDictionary *meta = [FLTImagePickerMetaDataUtil getMetaDataFromImageData:data];
   XCTAssertEqualObjects(meta[(__bridge NSString *)kCGImagePropertyExifDictionary]
-                            [(__bridge NSString *)kCGImagePropertyExifMakerNote],
+                            [(__bridge NSString *)kCGImagePropertyExifUserComment],
                         @"aNote");
 }