Fix a test error in autodiff_test.cc.

Previously, the test for the projective camera model would fail as no
tolerance is set in line 144. To resolve this, this commit changes
assert_equal to assert_near.

Change-Id: I6cd3379083b1a10c7cd0a9cc83fd6962bb993cc9

internal/ceres/autodiff_test.cc

diff --git a/internal/ceres/autodiff_test.cc b/internal/ceres/autodiff_test.cc
index 4049ad5..20f4437 100644
--- a/internal/ceres/autodiff_test.cc
+++ b/internal/ceres/autodiff_test.cc
@@ -185,7 +185,7 @@
                                                             fd_x, fd_J)));
 
   for (int i = 0; i < 2; ++i) {
-    ASSERT_EQ(fd_x[i], b_x[i]);
+    ASSERT_NEAR(fd_x[i], b_x[i], tol);
   }
 
   // Use automatic differentiation to compute the Jacobian.