Clarify the API stability wording
Clarify the API stability wording

Previously the wording implied that between major versions the API won't change.
But it's pretty clear from the surrounding wording and general semvar concept
that the API _will_ change between major versions... it's only between minor/patch
versions that it won't change.
rrosenblum/rubocop,tejasbubane/rubocop,tejasbubane/rubocop,rrosenblum/rubocop,rrosenblum/rubocop,tejasbubane/rubocop