Remove objcopy from ti_simplelink_executable (#5066)

The preceding comment says we don't actually need the image in ihex
format. So don't produce it.
diff --git a/third_party/ti_simplelink_sdk/ti_simplelink_executable.gni b/third_party/ti_simplelink_sdk/ti_simplelink_executable.gni
index f7ce948..0db5bdb 100644
--- a/third_party/ti_simplelink_sdk/ti_simplelink_executable.gni
+++ b/third_party/ti_simplelink_sdk/ti_simplelink_executable.gni
@@ -17,11 +17,6 @@
 import("${build_root}/toolchain/flashable_executable.gni")
 
 template("ti_simplelink_executable") {
-  # we really only need the ELF
-  objcopy_image_name = invoker.output_name + ".hex"
-  objcopy_image_format = "ihex"
-  objcopy = "arm-none-eabi-objcopy"
-
   flashable_executable(target_name) {
     forward_variables_from(invoker, "*")
   }