drop the old fetch behavior for pre Cargo 0.13.0

This behavior is flakey and doesn't work from Cargo 0.13.0 and newer
which aren't part of this repo anymore.

(cherry picked from commit 339cc787cc)

classes/cargo.bbclass

@@ -83,10 +83,6 @@ oe_cargo_fix_env () {
 EXTRA_OECARGO_PATHS ??= ""
 
 cargo_do_compile () {
-	# prevent cargo from trying to fetch down new data
-	mkdir -p "${WORKDIR}/cargo_home/registry/index/github.com-1ecc6299db9ec823"
-	touch "${WORKDIR}/cargo_home/registry/index/github.com-1ecc6299db9ec823/.cargo-index-lock"
-
 	oe_cargo_fix_env
 	oe_cargo_build
 }