Updating strings for Install unknown apps

Updating some strings for clarity based on ux review.

Test: Manual

Bug: 37362450
     37362065
Change-Id: I26dd191d19ea8f3bd905c2e61ff77c4a2b796b3c
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 236ec29..7fa9b27 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -7678,11 +7678,11 @@
     <!-- Summary of app not allowed to write system settings [CHAR LIMIT=45] -->
     <string name="write_settings_off">No</string>
     <!-- Summary of app trusted to install apps [CHAR LIMIT=45] -->
-    <string name="external_source_trusted">Yes</string>
+    <string name="external_source_trusted">Allowed</string>
     <!-- Summary of app not trusted to install apps [CHAR LIMIT=45] -->
-    <string name="external_source_untrusted">No</string>
+    <string name="external_source_untrusted">Not allowed</string>
     <!-- Title of switch preference that controls whether an external app source is trusted or not [CHAR LIMIT=50] -->
-    <string name="external_source_switch_title">Allow app installs</string>
+    <string name="external_source_switch_title">Allow from this source</string>
 
     <!-- Title of setting that controls gesture to open camera [CHAR LIMIT=40] -->
     <string name="camera_gesture_title">Double twist for camera</string>