Poison device memory allocations for GN MemorySanitizer builds

Bug: b/140991626
Change-Id: I2cfab54e74b0808609c3195287856261fefad955
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/58988
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>

src/Vulkan/BUILD.gn

diff --git a/src/Vulkan/BUILD.gn b/src/Vulkan/BUILD.gn
index f8db101..e20282c 100644
--- a/src/Vulkan/BUILD.gn
+++ b/src/Vulkan/BUILD.gn
@@ -53,7 +53,6 @@
 
   defines += [
      "SWIFTSHADER_ENABLE_ASTC",  # TODO(b/150130101)
-     "SWIFTSHADER_ZERO_INITIALIZE_DEVICE_MEMORY",  # TODO(b/140991626)
   ]
 }