Remove unecessary use of Str in DEPS

This trips up fetch_dependencies.py that doesn't add an Str function to
the evaluation environment. Since these Str calls are not necessary,
just remove them.

Bug: dawn:1928
Change-Id: Ic02f448d5818b5e50129507211f16fe1521cd738
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/143400
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
diff --git a/DEPS b/DEPS
index 4534e3b..1a394e4 100644
--- a/DEPS
+++ b/DEPS
@@ -36,10 +36,10 @@
   # Fetch configuration files required for the 'use_remoteexec' gn arg
   'download_remoteexec_cfg': False,
   # RBE instance to use for running remote builds
-  'rbe_instance': Str('projects/rbe-chrome-untrusted/instances/default_instance'),
+  'rbe_instance': 'projects/rbe-chrome-untrusted/instances/default_instance',
   # RBE project to download rewrapper config files for. Only needed if
   # different from the project used in 'rbe_instance'
-  'rewrapper_cfg_project': Str(''),
+  'rewrapper_cfg_project': '',
   # reclient CIPD package
   'reclient_package': 'infra/rbe/client/',
   # reclient CIPD package version