docs: Fix bad @code syntax in doc comment

A doc comment used the incorrect syntax (@code ...) (should be
curly braces, {@code ...}.

NO_TEST , fixes a doc bug (no code edits).

Staged the fixed doc to:

* go/dac-stage/reference/android/content/Context
* go/dac-stage/reference/kotlin/android/content/Context

Test: m -j 8 ds-docs-switched
Bug: 288173952
Change-Id: I891673e62225a724a9184470804d60f145b8acea