[webcrypto] Delete some deprecated code.
[webcrypto] Delete some deprecated code.

BUG=245025
TBR=abarth

Review URL: https://codereview.chromium.org/141073008

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@165478 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs