deps: Upgrade packages to latest, namely file_picker

This is the result of `flutter pub upgrade --major-versions`,
followed by `flutter build ios --config-only`.
(Plus `flutter build macos --config-only`, but it has no
effect, as file_picker doesn't appear in macos/Podfile.lock .)

Changelog:
  https://pub.dev/packages/file_picker/changelog

The API changes don't affect our usage.

Author: gnprice

ios/Podfile.lock

@@ -116,7 +116,7 @@ SPEC CHECKSUMS:
   device_info_plus: c6fb39579d0f423935b0c9ce7ee2f44b71b9fce6
   DKImagePickerController: b512c28220a2b8ac7419f21c491fc8534b7601ac
   DKPhotoGallery: fdfad5125a9fdda9cc57df834d49df790dbb4179
-  file_picker: ce3938a0df3cc1ef404671531facef740d03f920
+  file_picker: 15fd9539e4eb735dc54bae8c0534a7a9511a03de
   Flutter: f04841e97a9d0b0a8025694d0796dd46242b2854
   image_picker_ios: 4a8aadfbb6dc30ad5141a2ce3832af9214a705b5
   package_info_plus: 115f4ad11e0698c8c1c5d8a689390df880f47e85

pubspec.lock

@@ -301,10 +301,10 @@ packages:
     dependency: "direct main"
     description:
       name: file_picker
-      sha256: be325344c1f3070354a1d84a231a1ba75ea85d413774ec4bdf444c023342e030
+      sha256: "903dd4ba13eae7cef64acc480e91bf54c3ddd23b5b90b639c170f3911e489620"
       url: "https://pub.dev"
     source: hosted
-    version: "5.5.0"
+    version: "6.0.0"
   file_selector_linux:
     dependency: transitive
     description:

pubspec.yaml

@@ -47,7 +47,7 @@ dependencies:
   intl: ^0.18.0
   share_plus: ^7.0.0
   device_info_plus: ^9.0.0
-  file_picker: ^5.2.7
+  file_picker: ^6.0.0
   drift: ^2.5.0
   path_provider: ^2.0.13
   path: ^1.8.3