fix typo in error string

letsencrypt.sh

@@ -50,7 +50,7 @@ _request() {
     curl -sSf "${2}" -d "${3}" 2>"${temperr}"
   fi
   if [ -s "${temperr}" ]; then
-      echo "  + ERROR: An error occured while sending ${1}-request to ${2} ($(<"${temperr}"))" >&2
+      echo "  + ERROR: An error occurred while sending ${1}-request to ${2} ($(<"${temperr}"))" >&2
       rm -f "${temperr}"
       exit 1
   fi