[FIX] gpu approx nearest unit test

[chunibyo-wly]

This unit test failed due the precision.
The error log

/home/chunibyo/workspace/osc/pcl/test/gpu/octree/test_approx_nearest.cpp:129: Failure
Expected equality of these values:
  dists_pcl[i]
    Which is: 0.03
  dists_gpu[i]
    Which is: 0.03
[  FAILED  ] PCL_OctreeGPU.approxNearesSearch 

And we can see their binary representations are

00111100111101011100001010010111 (0.030000014)
00111100111101011100001010010110 (0.030000012)

[Copilot]

Pull request overview

This PR fixes a flaky/incorrect GPU octree unit test by comparing floating-point squared distances using a float-aware assertion rather than exact bitwise equality, addressing small ULP-level differences between CPU and GPU computations.

Changes:

• Replace ASSERT_EQ with ASSERT_FLOAT_EQ when comparing std::vector<float> distance results between CPU and GPU host paths.

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