Composer.json scripts do not support strings

[adamwillcock]

After moving from heroku/buildpacks:20 to heroku/builder:22, composer.json parsing fails when using strings in scripts. This is noted as valid syntax from Composer: https://getcomposer.org/doc/articles/scripts.md#defining-scripts

An event's scripts can be defined as either a string (only for a single script) or an array (for single or multiple scripts.)

[builder] 
[builder] [Error: Failed to parse 'composer.json']
[builder] The parsed contents were invalid.
[builder] 
[builder] Details: invalid type: string "phpcbf", expected a sequence at line 100 column 1
[builder] 
[builder] Please run 'composer validate' on your local computer for verification.
[builder] 
[builder] If you believe this message to be in error, please report it.
[builder] ERROR: failed to build: exit status 1
ERROR: failed to build: executing lifecycle. This may be the result of using an untrusted builder: failed with status code: 51

Example composer.json:

        "compile": [
            "bin/doctrine orm:generate-proxies"
        ],
        "cs": [
            "phpcs"
        ],
        "cs:fix": "phpcbf",
        "test": "phpunit",
        "test:ordered": [
            "phpunit --testsuite unit",
            "phpunit --testsuite functional"
        ],
        "serve": "php -S 0.0.0.0:8080 -t public/"
    }

This is resolved when moving the strings into arrays:

"cs:fix": [
    "phpcbf"
 ],