py3: add b'' prefixes in tests/test-extensions-afterloaded.t
# skip-blame because just b'' prefixes
Differential Revision: https://phab.mercurial-scm.org/D3596
py3: add b'' prefixes in tests/test-custom-filters.t
# skip-blame because just b'' prefixes
Differential Revision: https://phab.mercurial-scm.org/D3595