[shuffle] Remove the `utils::` namespace.

This CL strips the `utils::` namespace declaration and usages.

Bug: tint:1988
Change-Id: I860b9cae052bec9eed0879fdda6ff2a05534af0e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/143421
Auto-Submit: Dan Sinclair <dsinclair@chromium.org>
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: David Neto <dneto@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
diff --git a/src/tint/utils/file/tmpfile.h b/src/tint/utils/file/tmpfile.h
index ed83918..38cdf71 100644
--- a/src/tint/utils/file/tmpfile.h
+++ b/src/tint/utils/file/tmpfile.h
@@ -19,7 +19,7 @@
 
 #include "src/tint/utils/text/string_stream.h"
 
-namespace tint::utils {
+namespace tint {
 
 /// TmpFile constructs a temporary file that can be written to, and is
 /// automatically deleted on destruction.
@@ -56,7 +56,7 @@
     /// @return a reference to this TmpFile
     template <typename T>
     inline TmpFile& operator<<(T&& data) {
-        utils::StringStream ss;
+        StringStream ss;
         ss << data;
         std::string str = ss.str();
         Append(str.data(), str.size());
@@ -70,6 +70,6 @@
     std::string path_;
 };
 
-}  // namespace tint::utils
+}  // namespace tint
 
 #endif  // SRC_TINT_UTILS_FILE_TMPFILE_H_