Use correct info for Creator Organization in REUSE-generated source SBOMs

SPDXVersion: SPDX-2.1
DataLicense: CC0-1.0
SPDXID: SPDXRef-DOCUMENT
DocumentName: qtbase
DocumentNamespace: http://spdx.org/spdxdocs/spdx-v2.1-c755b969-dc44-4507-a3b0-bad614c0a41c
Creator: Person: Anonymous ()
Creator: Organization: Anonymous ()
Creator: Tool: reuse-5.0.2
Created: 2024-11-20T15:49:31Z
CreatorComment: <text>This document was created automatically using available reuse information consistent with REUSE.</text>

Creator: Person: Anonymous ()
Creator: Organization: Anonymous ()

SPDXVersion: SPDX-2.3
DataLicense: CC0-1.0
SPDXID: SPDXRef-DOCUMENT
DocumentName: qtbase-6.8.1
DocumentNamespace: https://qt.io/spdxdocs/qtbase-6.8.1
Creator: Organization: TheQtCompany
Creator: Tool: Qt Build System
CreatorComment: <text>This SPDX document was created from CMake 3.30.5, using the qt
build system from https://code.qt.io/cgit/qt/qtbase.git/tree/cmake/QtPublicSbomHelpers.cmake</text>
Created: 2024-11-20T15:08:22Z

$ reuse spdx --help
Usage: reuse spdx [OPTIONS]

  Generate an SPDX bill of materials.

Options:
  -o, --output FILENAME        File to write to.
  --add-license-concluded      Populate the LicenseConcluded field; note that
                               reuse cannot guarantee that the field is
                               accurate.
  --creator-person TEXT        Name of the person signing off on the SPDX
                               report.
  --creator-organization TEXT  Name of the organization signing off on the
                               SPDX report.
  --help