WebView: change 'iff' to 'if' in docs

Docs change only, no change to logic.

This replaces "iff" (if and only if) with "if". The former term is
unclear, and there's no real benefit to expanding to "if and only if."

Change-Id: I1ac26e24b816f784b6868c8860849d4118b33294
Fixes: 68133964
Test: make -j40 docs (manually verify the change looks good)