Docs: Update to clarify what's allowed for Trust Agent

Test: make_cdd.sh script
Change-Id: I7bf9bc3d0313ffc719f176eda3c80a9bd7b0d6c9

diff --git a/9_security-model/9_11_keys-and-credentials.md b/9_security-model/9_11_keys-and-credentials.md
index fe42b8f..a43fa24 100644
--- a/9_security-model/9_11_keys-and-credentials.md
+++ b/9_security-model/9_11_keys-and-credentials.md

@@ -168,7 +168,7 @@
 trust agent, which implements the `TrustAgentService` System API, they:
 
 *    [C-7-1] MUST have clear indication in the settings menu and on the lock
-     screen when device lock is deferred or can be unlocked by trust agent(s).
+     screen when device lock is deferred or can be kept unlocked by trust agent(s).
      For example, AOSP meets this requirement by showing a text description for
      the "Automatically lock setting" and "Power button instantly locks" in the
      settings menu and a distinguishable icon on the lock screen.