Prep to release 1.8.0-nullsafety.1

Reverts https://github.com/dart-lang/source_span/pull/59 and removes now unnecessary `!`s.

This requires a newer sdk than is available on dev, so run tests on be/raw/latest for now.

The dart version in flutter should already be compatible with this version.
4 files changed
tree: a6aa24f4257e86a3bbc80bd40e5f62553332cdef
  1. pkgs/