fetch: do not redundantly calculate tag refmap

builtin/fetch.c redundantly calculates refmaps for tags twice. Remove the first calculation. This is only a code simplification and slight performance improvement - the result is unchanged, as the redundant refmaps are subsequently removed by the invocation to "ref_remove_duplicates" anyway. This was introduced in commit c5a84e9 ("fetch --tags: fetch tags *in addition to* other stuff", 2013-10-29) when modifying the effect of the --tags parameter to "git fetch". The refmap-for-tag calculation was copied instead of moved. Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>