Merge branch 'fix/shallowwater-example-test' into 'master'

Fix/shallowwater example test

See merge request !1986 (merged)

(cherry picked from commit 77d04e3e)

24a7ad64 [examples][swe][fix] Update reference solution after change of boundary... 7c1ebb87 [examples][swe] Cleanup unused headers and improve BC