collision: update distance lower bound for sphere-sphere case

10 jobs for pr/230 in 35 minutes and 40 seconds (queued for 2 seconds)
Name Stage Failure
failed
robotpkg-py-hpp-fcl-py3-buster-release Test

Total Test time (real) = 47.69 sec

The following tests FAILED:
16 - gjk (Child aborted)
Errors while running CTest
make: *** [Makefile:110: test] Error 8
Cleaning up file based variables
ERROR: Job failed: exit code 1
failed
format Test
-}
+} // namespace fcl

-} // namespace hpp
+} // namespace hpp

#endif
Cleaning up file based variables
ERROR: Job failed: exit code 1