Update quiver dependency to 0.26.2 (#13299)

Updates quiver from 0.26.0 to 0.26.2 to pick up strong-mode fixes.
diff --git a/examples/flutter_gallery/pubspec.yaml b/examples/flutter_gallery/pubspec.yaml
index 4da5e75..588b13b 100644
--- a/examples/flutter_gallery/pubspec.yaml
+++ b/examples/flutter_gallery/pubspec.yaml
@@ -47,7 +47,7 @@
   path: 1.4.2 # TRANSITIVE DEPENDENCY
   pool: 1.3.3 # TRANSITIVE DEPENDENCY
   pub_semver: 1.3.2 # TRANSITIVE DEPENDENCY
-  quiver: 0.26.0 # TRANSITIVE DEPENDENCY
+  quiver: 0.26.2 # TRANSITIVE DEPENDENCY
   shelf: 0.7.1 # TRANSITIVE DEPENDENCY
   shelf_packages_handler: 1.0.3 # TRANSITIVE DEPENDENCY
   shelf_static: 0.2.6 # TRANSITIVE DEPENDENCY