feat: Update Cloud Functions samples to use non-EOL PHP

[bshaffer]

Some of our Cloud Functions samples still use PHP 7.4

• php-docs-samples/functions/helloworld_storage/composer.json

  Line 3 in add395f

  "php": ">= 7.4",

• php-docs-samples/functions/typed_greeting/composer.json

  Line 3 in add395f

  "php": ">= 7.4",

• php-docs-samples/functions/helloworld_pubsub/composer.json

  Line 3 in add395f

  "php": ">= 7.4",

• php-docs-samples/functions/helloworld_http/composer.json

  Line 3 in add395f

  "php": ">= 7.4",

As this version of PHP is now EOL, we need to upgrade these to the more current versions of PHP 8.2 or 8.3.