Humble branch does not contain file approximate_epsilon_time.h

[tamerlan-b]

The approximate_epsilon_time.hpp file (commit: a2dec47) including approximate_epsilon_time file.h has been added to the ROS2 Humble branch. However, the approximate_epsilon_time file.h is missing from the humble branch.

Also according to the ROS2 documentation, ApproximateEpsilonTime and LatestTime policies have been added since the ROS2 Iron distro.

One of the two things seems logical:

1. Either add the approximate_epsilon_time.h file to the humble branch
2. Or delete the approximate_epsilon_time file.hpp from the humble branch