Fix incorrect version constraint from d7de06f (#196)

diff --git a/pubspec.yaml b/pubspec.yaml
index b319c1a..e777a8c 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -18,8 +18,8 @@
   test_api: ^0.2.1
 
 dev_dependencies:
-  build_runner: '>=1.0.0 <3.0.0'
+  build_runner: ^1.0.0
   build_test: ^0.10.0
-  build_web_compilers: ^1.0.0
+  build_web_compilers: '>=1.0.0 <3.0.0'
   pedantic: ^1.3.0
   test: ^1.5.1