chore(internal): fix release workflows

Author: stainless-app[bot]

bin/check-release-environment

@@ -2,6 +2,10 @@
 
 errors=()
 
+if [ -z "${STAINLESS_API_KEY}" ]; then
+  errors+=("The STAINLESS_API_KEY secret has not been set. Please contact Stainless for an API key & set it in your organization secrets on GitHub.")
+fi
+
 if [ -z "${SONATYPE_USERNAME}" ]; then
   errors+=("The OPENAI_SONATYPE_USERNAME secret has not been set. Please set it in either this repository's secrets or your organization secrets")
 fi