Remove config_telephony_use_own_number_for_voicemail

Remove this overlay value which was removed in the
base overlay config.

Bug: 65683508
Test: compilation
Change-Id: I38a7ec36803c3d4ac0899d1564775c5554545798
diff --git a/overlay/frameworks/base/core/res/res/values-mcc310-mnc120/config.xml b/overlay/frameworks/base/core/res/res/values-mcc310-mnc120/config.xml
index 9ad99e4..b173860 100755
--- a/overlay/frameworks/base/core/res/res/values-mcc310-mnc120/config.xml
+++ b/overlay/frameworks/base/core/res/res/values-mcc310-mnc120/config.xml
@@ -43,9 +43,6 @@
     <!-- Sprint's WAP push PDU is special, should set the index -->
     <integer name="config_valid_wappush_index">4</integer>
 
-    <!-- The VoiceMail default value is displayed to my own number if it is true -->
-    <bool name="config_telephony_use_own_number_for_voicemail">true</bool>
-
     <!-- Default network policy warning threshold, in megabytes. -->
     <integer name="config_networkPolicyDefaultWarning">51200</integer>