change version to 2.0.15.1

Author: xiaokang

gensrc/script/gen_build_version.sh

@@ -31,7 +31,7 @@ build_version_prefix="doris"
 build_version_major=2
 build_version_minor=0
 build_version_patch=15
-build_version_rc_version=""
+build_version_rc_version="1"
 
 if [[ -z "${build_version_rc_version}" ]]; then
     build_version="${build_version_prefix}-${build_version_major}.${build_version_minor}.${build_version_patch}"