kbuild: remove unused quiet_cmd_update_lto_symversions

This is not used anywhere because the short log is displayed when
it is used through a $(call cmd,...) invocation.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>

scripts/Makefile.build

@@ -406,7 +406,6 @@ $(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ;
 $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
 
 # combine symversions for later processing
-quiet_cmd_update_lto_symversions = SYMVER  $@
 ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
       cmd_update_lto_symversions =					\
 	rm -f $@.symversions						\