Remove unneeded airplane mode strings

Wifi tether doesn't care about airplane more anymore so we don't
need these.

Test: robotests pass
Bug: 111681176
Change-Id: Icf2cc8c944dc9e2c6f7bdf11478a2772292ea913
diff --git a/res/values/strings.xml b/res/values/strings.xml
index b912c9d..6976601 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -2390,8 +2390,6 @@
     <string name="wifi_hotspot_configure_ap_text_summary">AndroidAP WPA2 PSK hotspot</string>
     <!-- Default access point SSID used for tethering -->
     <string name="wifi_tether_configure_ssid_default">AndroidHotspot</string>
-    <!-- Summary text when hotspot is disabled because airplane mode is on [CHAR LIMIT=80]-->
-    <string name="wifi_tether_disabled_by_airplane">Unavailable because airplane mode is turned on</string>
 
     <!-- Do not translate. Used for diagnostic screens, precise translation is not necessary
          Wi-Fi Testing on the diagnostic screen-->