Language update

The following term(s) that should be avoided:

- [ ] grandfathered -> legacy

- [ ] whitelist -> allowlist

- [ ] master -> main

These were found in the following file(s):
```
nototools/notodiff.py

nototools/data/familyname_and_styles.txt

nototools/noto_lint.py

nototools/unittests/font_tests.py

nototools/shape_diff.py

nototools/update_udhr_samples.py
```