ci: Do not set CARGO_NET_GIT_FETCH_WITH_CLI in Cirrus CI

Author: taiki-e

.cirrus.yml

@@ -2,7 +2,6 @@ only_if: $CIRRUS_TAG == '' && ($CIRRUS_PR != '' || $CIRRUS_BRANCH == 'main' || $
 auto_cancellation: $CIRRUS_PR != ''
 env:
   CARGO_INCREMENTAL: '0'
-  CARGO_NET_GIT_FETCH_WITH_CLI: 'true'
   CARGO_NET_RETRY: '10'
   CARGO_TERM_COLOR: always
   RUST_BACKTRACE: '1'