allow test_core version 5.x (#3477)

Author: jakemac53

build_test/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.1.7
+
+- Allow the latest test_core (version 5.x).
+
 ## 2.1.6
 
 - Fix bug in package config file loading.

build_test/pubspec.yaml

@@ -1,6 +1,6 @@
 name: build_test
 description: Utilities for writing unit tests of Builders.
-version: 2.1.6
+version: 2.1.7
 repository: https://github.com/dart-lang/build/tree/master/build_test
 
 environment:
@@ -20,7 +20,7 @@ dependencies:
   path: ^1.8.0
   stream_transform: ^2.0.0
   test: ^1.16.0
-  test_core: '>=0.3.19 <0.5.0'
+  test_core: '>=0.3.19 <0.6.0'
   watcher: ^1.0.0
 
 dev_dependencies: