This check adds a few constraints on the way to build a project when we have
a proto file which imports another one. In particular, on projects which
build both C# and Java, it's easy to end up with exceptions like

    Expected: included.proto but was src/main/protobuf/included.proto

A user may work around this issue, but it may add unnecessary constraints
on the layout of the project.

According to https://github.com/google/protobuf/commit/f3504cf3b1d456a843e8242fdee9ba0bf2991dc1#diff-ecb0b909ed572381a1c8d1994f09a948R309
it has already been considered to get rid of this check, for
similar considerations, and because it doesn't exist in the Java code