Remove redundant CMAKE_CXX_STANDARD assignment

Change-Id: Ie629a4c9f0a83e9c92b98dbaacf0bc8cde0f41b3
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/194911
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jaswant Panchumarti <jaswant.panchumarti@kitware.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1b70488..7538491 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -396,8 +396,6 @@
     target_compile_definitions(dawn_internal_config INTERFACE "NOMINMAX" "WIN32_LEAN_AND_MEAN")
 endif()
 
-set(CMAKE_CXX_STANDARD "17")
-
 ################################################################################
 # Tint
 ################################################################################