Upgrade AWS sdk to 2.7.5

apps/files_external/3rdparty/aws-sdk-php/Aws/Common/Aws.php

...3rdparty/aws-sdk-php/Aws/Common/Client/AbstractClient.php

.../3rdparty/aws-sdk-php/Aws/Common/Client/ClientBuilder.php

..._external/3rdparty/aws-sdk-php/Aws/Common/Enum/Region.php

...ternal/3rdparty/aws-sdk-php/Aws/Common/Hash/HashUtils.php

...ws/Common/Model/MultipartUpload/AbstractUploadBuilder.php

.../3rdparty/aws-sdk-php/Aws/Common/Resources/aws-config.php

...rty/aws-sdk-php/Aws/Common/Resources/public-endpoints.php

...3rdparty/aws-sdk-php/Aws/Common/RulesEndpointProvider.php

...3rdparty/aws-sdk-php/Aws/Common/Signature/SignatureV4.php

.../files_external/3rdparty/aws-sdk-php/Aws/S3/Model/Acp.php

...external/3rdparty/aws-sdk-php/Aws/S3/Model/AcpBuilder.php

...xternal/3rdparty/aws-sdk-php/Aws/S3/Model/ClearBucket.php

.../3rdparty/aws-sdk-php/Aws/S3/Model/DeleteObjectsBatch.php

...dparty/aws-sdk-php/Aws/S3/Model/DeleteObjectsTransfer.php

...iles_external/3rdparty/aws-sdk-php/Aws/S3/Model/Grant.php

...es_external/3rdparty/aws-sdk-php/Aws/S3/Model/Grantee.php

...ws-sdk-php/Aws/S3/Model/MultipartUpload/UploadBuilder.php

...l/3rdparty/aws-sdk-php/Aws/S3/Resources/s3-2006-03-01.php

apps/files_external/3rdparty/aws-sdk-php/Aws/S3/S3Client.php