Update git-ref to generator

Update the git-ref to the discovery_api_dart_client_generator package to
pick up

  https://codereview.chromium.org//648623002
  https://codereview.chromium.org//647653003

R=kustermann@google.com
BUG=

Review URL: https://codereview.chromium.org//673163002
diff --git a/pubspec.lock b/pubspec.lock
index 9b83f79..1a3c3c2 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -15,8 +15,8 @@
     version: "0.9.0"
   discovery_api_client_generator:
     description:
-      ref: "357ad269094094ce0b6a4b8316ddc75f3fb7f23c"
-      resolved-ref: "357ad269094094ce0b6a4b8316ddc75f3fb7f23c"
+      ref: "105b08834192078569c8a76e0a92bcce7f25ae5f"
+      resolved-ref: "105b08834192078569c8a76e0a92bcce7f25ae5f"
       url: "https://github.com/dart-lang/discovery_api_dart_client_generator"
     source: git
     version: "0.5.1-dev"
diff --git a/pubspec.yaml b/pubspec.yaml
index 8d330a8..3aea889 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -6,5 +6,5 @@
   discovery_api_client_generator:
     git:
       url: https://github.com/dart-lang/discovery_api_dart_client_generator
-      ref: 357ad269094094ce0b6a4b8316ddc75f3fb7f23c
+      ref: 105b08834192078569c8a76e0a92bcce7f25ae5f
     version: ">=0.5.0 <0.6.0"