Create dist clones without a specified branch

Specifying the release candidate version results in the final release
referencing the release candidate tag, which would be an odd quirk.
Instead, release procedures should specify that releases be made from
release branches and release testing procedures should contain
instructions for checking the branch name.

Makefile

@@ -63,7 +63,6 @@ else
 dist:
 	@rm -rf apache-annotator-$(annotator_vsn)-incubating
 	@git clone \
-        --branch v$(vsn_tag) \
         --config advice.detachedHead=false \
         --depth 1 \
         --quiet \