Remove text saying restoring the default dialer is optional

If the default dialer is not restored, the Telecom CTS verifier tests
will not function correctly.

Change-Id: I03d8fc888e6649cddac9f74327c7d1737c263a5f
Fixes: 64072605
Test: string change
diff --git a/apps/CtsVerifier/res/values/strings.xml b/apps/CtsVerifier/res/values/strings.xml
index 8dd62b5..76a4fa3 100755
--- a/apps/CtsVerifier/res/values/strings.xml
+++ b/apps/CtsVerifier/res/values/strings.xml
@@ -3773,8 +3773,8 @@
     </string-array>
 
     <!-- Strings for setting and restoring default dialer for voicemail tests -->
-    <string name="voicemail_restore_default_dialer_description">(Optional) restore the default dialer setting</string>
-    <string name="voicemail_restore_default_dialer_no_default_description">(Optional) restore the default dialer by going to settings-> apps -> cogwheel -> Phone app</string>
+    <string name="voicemail_restore_default_dialer_description">Restore the default dialer setting</string>
+    <string name="voicemail_restore_default_dialer_no_default_description">Restore the default dialer by going to settings-> apps -> cogwheel -> Phone app</string>
     <string name="voicemail_restore_default_dialer_button">Restore the default dialer"</string>
     <string name="voicemail_default_dialer_already_set">Default dialer already set</string>
     <string name="voicemail_default_dialer_already_restored">Default dialer already restored</string>