docs: Fixing broken HTML

A couple of broken </code> tags were messing up the formatting
for the entire page (see b/134696600 , http://screen/aThdcpoDvJo.png )

Staged the fixed doc to:

http://go/dac-stage/reference/android/app/Activity

(The live version of this doc has already been fixed -- I fixed
the HTML by hand in cl/251937759 -- but we need to fix the Java
comment, or the file will revert when we publish beta 5.)

Bug: 134696600
Test: make ds-docs (& staged HTML output)
Exempt-From-Owner-Approval: Docs-only fix
Change-Id: I7e6d11ca358d747cdc6d04741d31c7acd85aa080

core/java/android/app/Activity.java

@@ -2330,7 +2330,7 @@ public class Activity extends ContextThemeWrapper
      * calling {@link VoiceInteractor#notifyDirectActionsChanged()}.
      *
      * <p>To get the voice interactor you need to call {@link #getVoiceInteractor()}
-     * which would return non <code>null<c/ode> only if there is an ongoing voice
+     * which would return non <code>null</code> only if there is an ongoing voice
      * interaction session. You an also detect when the voice interactor is no
      * longer valid because the voice interaction session that is backing is finished
      * by calling {@link VoiceInteractor#registerOnDestroyedCallback(Executor, Runnable)}.
@@ -2339,7 +2339,7 @@ public class Activity extends ContextThemeWrapper
      * before {@link #onStop()} is being called.
      *
      * <p>You should pass to the callback the currently supported direct actions which
-     * cannot be <code>null</code> or contain <code>null</null> elements.
+     * cannot be <code>null</code> or contain <code>null</code> elements.
      *
      * <p>You should return the action list as soon as possible to ensure the consumer,
      * for example the assistant, is as responsive as possible which would improve user