Re-write persist.sh file in one line

There is a php command we can use to dump OpenAPI spec,
and then paste it in our docs/openapi.json:

`php bin/console api:openapi:export > docs/openapi.json`

docs/persist.sh

@@ -1,32 +1,6 @@
 #!/bin/sh
 
-# Default values
-default_url=https://localhost/docs.json
-default_output_file_path="docs/openapi.json"
+# About api:openapi:export:
+# Dump the Open API documentation
 
-url="${1:-$default_url}"
-output_file_path="${2:-$default_output_file_path}"
-
-# Use curl to fetch the JSON data from the provided URL
-json_data=$(curl -s -k "$url" | jq)
-
-# Check if the curl command was successful
-if [ $? -ne 0 ]; then
-  echo "Failed to fetch JSON data from $url"
-  exit 1
-fi
-
-# Write the JSON data to the specified output file
-echo "$json_data" > "$output_file_path"
-
-# Check if the write operation was successful
-if [ $? -ne 0 ]; then
-  echo "Failed to write JSON data to $output_file_path"
-  exit 1
-fi
-
-echo "JSON data successfully copied from $url to $output_file_path"
-
-# how to use it:
-# bash docs/persist.sh "http://example.com.docs.json" "docs/test.json"
-# or with default values: bash docs/persist.sh
+docker compose exec php bin/console api:openapi:export > docs/openapi.json