Fix @deprecated javadoc tags inside {@code} blocks.

Metalava incorrectly interpreted "@deprecated" javadoc tags inside
{@code} blocks and added @Deprecated annotation to class when it
shouldn't.

The fix is to use the HTML escape sequence for "@" character inside
{@code} blocks.

Bug: 180965011
Test: m art.module.public.api.stubs.source-update-current-api
Change-Id: I54f6de861528c6f611598dd34a4480d9302979cb
2 files changed