fix: use correct set output syntax

FloXire · vadi2 · commit 7deec762169d · 2022-02-03T06:29:46.000+01:00
diff --git a/entrypoint.sh b/entrypoint.sh
@@ -2,4 +2,4 @@
 set -e
 
 output=$(xmlstarlet $@)
-echo "::set_output name=xmlstarlet_result::${output}"
+echo "::set-output name=xmlstarlet_result::${output}"
