Remove mojo/tools/, not needed in chromium

mojo/BUILD.gn

Index: mojo/BUILD.gn
diff --git a/mojo/BUILD.gn b/mojo/BUILD.gn
index 63fee4c17bc68b1f7eb6149a4543944d7b23a301..38fe53b39970c56c7142b731bbf25e4e13f9e579 100644
--- a/mojo/BUILD.gn
+++ b/mojo/BUILD.gn
@@ -12,7 +12,6 @@ group("mojo") {
     "//mojo/common",
     "//mojo/public",
     "//mojo/services",
-    "//mojo/tools/package_manager",
   ]
 
   if (is_android) {
@@ -37,6 +36,5 @@ group("tests") {
     "//mojo/public/cpp/environment/tests:mojo_public_environment_unittests",
     "//mojo/public/cpp/system/tests:mojo_public_system_unittests",
     "//mojo/public/cpp/utility/tests:mojo_public_utility_unittests",
-    "//mojo/tools:message_generator",
   ]
 }