Remove unused metadata in DEPS from vuln scanning (#48995)

These upstream links (used in vulnerability scanning) are not needed since the references to the deps are no longer used. 
Part of simplifying metadata for the vuln scan process, context in b/248564768.

*If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].*

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: sealesj

DEPS

@@ -169,7 +169,6 @@ vars = {
   "upstream_file": "https://github.com/google/file.dart.git",
   "upstream_fixnum": "https://github.com/dart-lang/fixnum.git",
   "upstream_flatbuffers": "https://github.com/google/flatbuffers.git",
-  "upstream_fontconfig": "https://gitlab.freedesktop.org/fontconfig/fontconfig.git",
   "upstream_freetype2": "https://gitlab.freedesktop.org/freetype/freetype.git",
   "upstream_gcloud": "https://github.com/dart-lang/gcloud.git",
   "upstream_glfw": "https://github.com/glfw/glfw.git",
@@ -201,7 +200,6 @@ vars = {
   "upstream_matcher": "https://github.com/dart-lang/matcher.git",
   "upstream_mime": "https://github.com/dart-lang/mime.git",
   "upstream_mockito": "https://github.com/dart-lang/mockito.git",
-  "upstream_oauth2": "https://github.com/dart-lang/oauth2.git",
   "upstream_ocmock": "https://github.com/erikdoe/ocmock.git",
   "upstream_package_config": "https://github.com/dart-lang/package_config.git",
   "upstream_packages": "https://github.com/flutter/packages.git",
@@ -239,7 +237,6 @@ vars = {
   "upstream_typed_data": "https://github.com/dart-lang/typed_data.git",
   "upstream_usage": "https://github.com/dart-lang/usage.git",
   "upstream_vector_math": "https://github.com/google/vector_math.dart.git",
-  "upstream_Vulkan-Headers": "https://github.com/KhronosGroup/Vulkan-Headers.git",
   "upstream_VulkanMemoryAllocator": "https://github.com/GPUOpen-LibrariesAndSDKs/VulkanMemoryAllocator.git",
   "upstream_watcher": "https://github.com/dart-lang/watcher.git",
   "upstream_web_socket_channel": "https://github.com/dart-lang/web_socket_channel.git",