Fix MacOS compatibility script syntax (#4459)

Author: pchila

dev-tools/packaging/templates/darwin/elastic-agent.tmpl

@@ -9,6 +9,7 @@ if test -L "$symlink"; then
     symlinkTarget="data/elastic-agent-{{ commit_short }}/elastic-agent.app/Contents/MacOS/elastic-agent"
     if test -f "data/elastic-agent-{{ agent_package_version }}{{ snapshot_suffix }}-{{ commit_short }}/elastic-agent.app/Contents/MacOS/elastic-agent"; then
         symlinkTarget="data/elastic-agent-{{ agent_package_version }}{{ snapshot_suffix }}-{{ commit_short }}/elastic-agent.app/Contents/MacOS/elastic-agent"
+    fi
     ln -sfn "$symlinkTarget" "$symlink"
 fi