Update aws/aws-sdk-php requirement from ^3.237.1 to ^3.238.3

Updates the requirements on [aws/aws-sdk-php](https://github.com/aws/aws-sdk-php) to permit the latest version.
- [Release notes](https://github.com/aws/aws-sdk-php/releases)
- [Commits](aws/aws-sdk-php@3.237.1...3.238.3)

---
updated-dependencies:
- dependency-name: aws/aws-sdk-php
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

composer.json

@@ -11,7 +11,7 @@
  ],
  "require": {
  "php": ">=7.1",
- "aws/aws-sdk-php": "^3.237.1",
+ "aws/aws-sdk-php": "^3.238.3",
  "composer-plugin-api": "^1.1 || ^2.0",
  "composer/installers": "^1.12 || ^2.0",
  "segmentio/analytics-php": "~2.0.0"