Fix @code escapes

The body of {@code} must not be HTML escaped. This is one of
several changes that fix the source in conjunction with a
doclava fix.

Bug: 25757239
(cherry-picked from commit 385cccb8927b54284505b0bfdadb95e157cbdfd2)

Change-Id: I46010aa3937c227f359f8b73e802cd268ed7f483
15 files changed