Updated release tag format in the release script to use the new 0.12.0-rc1 style formatting.

Review: https://reviews.apache.org/r/11786
diff --git a/support/release.sh b/support/release.sh
index ef651a2..6d1b5c8 100755
--- a/support/release.sh
+++ b/support/release.sh
@@ -58,8 +58,8 @@
 
 echo "${GREEN}Now we'll create a git tag ...${NORMAL}"
 
-MESSAGE="Tag for release-${VERSION}-incubating-RC${CANDIDATE}."
-TAG="release-${VERSION}-incubating-RC${CANDIDATE}"
+MESSAGE="Tag for ${VERSION}-rc${CANDIDATE}."
+TAG="${VERSION}-rc${CANDIDATE}"
 git tag -m "${MESSAGE}" ${TAG} || \
   { echo "${RED}Failed to create git tag${NORMAL}"; exit 1; }