Remove Microsoft Corporation copyright from AGENTS.md and CLAUDE.md (#7932)

## Summary
- Remove the `# Copyright (c) Microsoft Corporation.` line from the
license header template in both AGENTS.md and CLAUDE.md
- The project license header should only contain the SPDX identifier and
team attribution

## Test plan
- [x] Verify AGENTS.md and CLAUDE.md no longer reference Microsoft
Corporation copyright

Signed-off-by: Zhipeng Wang <zwanga@wustl.edu>
Co-authored-by: Zhipeng Wang <zwanga@wustl.edu>
Co-authored-by: Olatunji Ruwase <tunji.ruwase@snowflake.com>

Author: 3 people

AGENTS.md

@@ -11,7 +11,6 @@
 - `check-torchdist` hook: NEVER directly import torch's distributed module. Use `import deepspeed.comm as dist` instead.
 - New files require license header:
   ```
-  # Copyright (c) Microsoft Corporation.
   # SPDX-License-Identifier: Apache-2.0
   # DeepSpeed Team
   ```

CLAUDE.md

@@ -11,7 +11,6 @@
 - `check-torchdist` hook: NEVER directly import torch's distributed module. Use `import deepspeed.comm as dist` instead.
 - New files require license header:
   ```
-  # Copyright (c) Microsoft Corporation.
   # SPDX-License-Identifier: Apache-2.0
   # DeepSpeed Team
   ```