fix camera test
fix camera test

Summary:
Fix a compilation error caused by unsupported `ASSERT_EQ` for matrices in `camera_test.cc`.
This DIFF replaces the affected ASSERTS by `ASSERT_TRUE(mat1.isApprox(mat2))`.

Reviewed By: paulinus

Differential Revision: D23758394

fbshipit-source-id: 50709348efabc654daf16d029c75e84af012d414

mapillary/OpenSfM,oscarlorentzon/OpenSfM,mapillary/OpenSfM,oscarlorentzon/OpenSfM,oscarlorentzon/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM,oscarlorentzon/OpenSfM,oscarlorentzon/OpenSfM