Remove unused dep on package:stack_trace (dart-lang/test_descriptor#26)

pkgs/test_descriptor/pubspec.yaml

diff --git a/pkgs/test_descriptor/pubspec.yaml b/pkgs/test_descriptor/pubspec.yaml
index 08a3192..0931981 100644
--- a/pkgs/test_descriptor/pubspec.yaml
+++ b/pkgs/test_descriptor/pubspec.yaml
@@ -13,7 +13,6 @@
   matcher: '^0.12.0'
   meta: '^1.1.7'
   path: '^1.0.0'
-  stack_trace: '^1.0.0'
   test: '^1.6.0'
   term_glyph: '^1.0.0'