[Bugfix] Use cmake 3.26.1 instead of 3.26 to avoid build failure

[houseroad]

To address #18748

Test plan:

Verified with cmake 3.26.0 (problematic), 3.26.1, 3.27.9, 3.30.5, 4.0.2. All others are good, only 3.26.0 only generate _C.so, not _C.abi3.so.

python setup.py develop with cmake==3.26.0

-- Install configuration: "RelWithDebInfo"
-- Installing: /home/lufang/gitrepos/vllm/build/lib.linux-x86_64-cpython-310/vllm/_moe_C.so
-- Set runtime path of "/home/lufang/gitrepos/vllm/build/lib.linux-x86_64-cpython-310/vllm/_moe_C.so" to ""
-- Install configuration: "RelWithDebInfo"
-- Installing: /home/lufang/gitrepos/vllm/build/lib.linux-x86_64-cpython-310/vllm/_rocm_C.so
-- Set runtime path of "/home/lufang/gitrepos/vllm/build/lib.linux-x86_64-cpython-310/vllm/_rocm_C.so" to ""
-- Install configuration: "RelWithDebInfo"
-- Installing: /home/lufang/gitrepos/vllm/build/lib.linux-x86_64-cpython-310/vllm/_C.so
-- Set runtime path of "/home/lufang/gitrepos/vllm/build/lib.linux-x86_64-cpython-310/vllm/_C.so" to ""
error: can't copy 'build/lib.linux-x86_64-cpython-310/vllm/_moe_C.abi3.so': doesn't exist or not a regular file

python setup.py develop with cmake>=3.26.1

Using /home/lufang/gitrepos/vllm/.venv/lib/python3.10/site-packages
Finished processing dependencies for vllm==0.9.1.dev108+g432ec9926.d20250602.rocm631

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[mgoin]

Thanks for tracking this down, LGTM. FYI @bnellnm