Update documentation for KEY_CARRIER_NAME_STRING

The documentation for KEY_CARRIER_NAME_STRING was out
of date; documentation updated to support the additional
use case of "fallback" carrier name when SPN is
unavailable.

Bug: 71882065
Test: compilation (docstring-only change)
Change-Id: I8e6a44358f8b18384c3c6e3cc0964e94c2484a11
diff --git a/telephony/java/android/telephony/CarrierConfigManager.java b/telephony/java/android/telephony/CarrierConfigManager.java
index 0a8d9cb..03a3ddb 100644
--- a/telephony/java/android/telephony/CarrierConfigManager.java
+++ b/telephony/java/android/telephony/CarrierConfigManager.java
@@ -950,8 +950,9 @@
     public static final String KEY_CARRIER_NAME_OVERRIDE_BOOL = "carrier_name_override_bool";
 
     /**
-     * String to identify carrier name in CarrierConfig app. This string is used only if
-     * #KEY_CARRIER_NAME_OVERRIDE_BOOL is true
+     * String to identify carrier name in CarrierConfig app. This string overrides SPN if
+     * #KEY_CARRIER_NAME_OVERRIDE_BOOL is true; otherwise, it will be used if its value is provided
+     * and SPN is unavailable
      * @hide
      */
     public static final String KEY_CARRIER_NAME_STRING = "carrier_name_string";