Merge redundant strings.

briar-android/src/main/res/layout-land/fragment_keyagreement_id.xml

@@ -32,7 +32,7 @@
 				android:layout_width="0dp"
 				android:layout_height="wrap_content"
 				android:layout_margin="16dp"
-				android:text="@string/add_contact_intro_two_way"
+				android:text="@string/info_both_must_scan"
 				app:layout_constraintEnd_toStartOf="@+id/guideline"
 				app:layout_constraintStart_toStartOf="parent"
 				app:layout_constraintTop_toBottomOf="@+id/diagram" />

briar-android/src/main/res/layout/fragment_keyagreement_id.xml

@@ -34,7 +34,7 @@
 				android:id="@+id/introTwoWay"
 				android:layout_width="match_parent"
 				android:layout_height="wrap_content"
-				android:text="@string/add_contact_intro_two_way"
+				android:text="@string/info_both_must_scan"
 				app:layout_constraintEnd_toEndOf="parent"
 				app:layout_constraintStart_toStartOf="parent"
 				app:layout_constraintTop_toBottomOf="@+id/diagram" />

briar-android/src/main/res/values/strings.xml

@@ -241,8 +241,7 @@
 	<!-- Adding Contacts -->
 
 	<string name="add_contact_title">Add Contact Nearby</string>
-	<string name="add_contact_intro_two_way">Both of you need to scan each other\'s QR code.</string>
-	<string name="add_contact_error_two_way">Did both of you scan each other\'s QR code?</string>
+	<string name="add_contact_error_two_way">Did you both scan each other\'s QR codes?</string>
 	<string name="face_to_face">You must meet up with the person you want to add as a contact.\n\nThis will prevent anyone from impersonating you or reading your messages in future.</string>
 	<string name="continue_button">Continue</string>
 	<string name="try_again_button">Try Again</string>