Exclude SPDX copyright lines from .clang-format

[achirkin]

NVIDIA's full copyright notice may exceed ColumnLimit: 100 and cause clang-format to corrupt the header for multi-year files.
This PR excludes the copyright line from clang-format checks to workaround this problem.

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[achirkin]

Note, the error was first encountered in #2237 , which now includes the same fix to test it.
Here's how the CI looks with the error:

clang-format.............................................................Failed
- hook id: clang-format
- files were modified by this hook
...
verify-copyright-cuvs....................................................Failed
- hook id: verify-copyright
- exit code: 1
- files were modified by this hook

In file cpp/src/neighbors/detail/cagra/compute_distance.hpp:2:28:
  * SPDX-FileCopyrightText: Copyright (c) 2023-2026, NVIDIA CORPORATION &
AFFILIATES. All rights
warning: copyright notice does not match canonical notice

In file cpp/src/neighbors/detail/cagra/compute_distance.hpp:2:28:
- * SPDX-FileCopyrightText: Copyright (c) 2023-2026, NVIDIA CORPORATION &
AFFILIATES. All rights
+ * SPDX-FileCopyrightText: Copyright (c) 2023-2026, NVIDIA CORPORATION &
AFFILIATES. All rights reserved.
note: suggested fix applied

[cjnolet]

/merge