Remove the RTT info panel when not needed

When device or carrier doesn't support RTT, don't show the panel that
gives information on what RTT is.

Bug: 76156715
Test: manual
Change-Id: I33781665416ba97df2680a15fda47b8f57ecb4e4
diff --git a/src/com/android/phone/settings/AccessibilitySettingsFragment.java b/src/com/android/phone/settings/AccessibilitySettingsFragment.java
index 8ec747c..314d895 100644
--- a/src/com/android/phone/settings/AccessibilitySettingsFragment.java
+++ b/src/com/android/phone/settings/AccessibilitySettingsFragment.java
@@ -44,6 +44,7 @@
     private static final String BUTTON_TTY_KEY = "button_tty_mode_key";
     private static final String BUTTON_HAC_KEY = "button_hac_key";
     private static final String BUTTON_RTT_KEY = "button_rtt_key";
+    private static final String RTT_INFO_PREF = "button_rtt_more_information_key";
 
     private final PhoneStateListener mPhoneStateListener = new PhoneStateListener() {
         /**
@@ -110,6 +111,8 @@
             mButtonRtt.setChecked(rttOn);
         } else {
             getPreferenceScreen().removePreference(mButtonRtt);
+            Preference rttInfoPref = findPreference(RTT_INFO_PREF);
+            getPreferenceScreen().removePreference(rttInfoPref);
             mButtonRtt = null;
         }
     }