Fix riscv toolchain promotion script typo

Change-Id: Ia796305034be61cbffac7a3d05b415bdcef3ac77

manage-riscv-toolchain.sh

diff --git a/manage-riscv-toolchain.sh b/manage-riscv-toolchain.sh
index df92dfd..66537ef 100755
--- a/manage-riscv-toolchain.sh
+++ b/manage-riscv-toolchain.sh
@@ -137,7 +137,7 @@
         "${PUBLIC_ARTIFACTS_PATH}/${tarball_name}.tar.gz"
     try gsutil cp \
         "${PUBLIC_ARTIFACTS_PATH}/toolchain_backups/${promote_tarball}.sha256sum" \
-        "${PUBLIC_ARTIFACTS_PATH}/${tarball_name}.tar.gz.256sum"
+        "${PUBLIC_ARTIFACTS_PATH}/${tarball_name}.tar.gz.sha256sum"
 }
 
 function main {