Remove COMMAND_CODE_CUSTOM from test controller app

This was added in 697759b
based on the assumption it had previously been missing, but actually it
is deliberately not included here because it must not be queried against
available session commands, as done here:
https://github.com/androidx/media/blob/839c4a90f2ab36e48be73e1b5e907f3283dce72e/testapps/controller/src/main/java/androidx/media3/testapp/controller/MediaAppControllerActivity.kt#L299

PiperOrigin-RevId: 756740269

Author: icbaker

testapps/controller/src/main/java/androidx/media3/testapp/controller/MediaIntToString.kt

@@ -67,7 +67,6 @@ object MediaIntToString {
     )
   val sessionCommandMap =
     mapOf(
-      SessionCommand.COMMAND_CODE_CUSTOM to "COMMAND_CUSTOM",
       SessionCommand.COMMAND_CODE_SESSION_SET_RATING to "COMMAND_SESSION_SET_RATING",
       SessionCommand.COMMAND_CODE_LIBRARY_GET_LIBRARY_ROOT to "COMMAND_LIBRARY_GET_LIBRARY_ROOT",
       SessionCommand.COMMAND_CODE_LIBRARY_SUBSCRIBE to "COMMAND_LIBRARY_SUBSCRIBE",

testapps/controller/src/test/java/androidx/media3/testapp/controller/MediaIntToStringTest.kt

@@ -42,9 +42,9 @@ class MediaIntToStringTest {
   @Test
   fun getSessionCommandMap() {
     val expectedSessionCommandMap =
-      getValuesToFieldNameMap(SessionCommand::class.java, "COMMAND_").mapValues { (_, value) ->
-        value.replace("COMMAND_CODE_", "COMMAND_")
-      }
+      getValuesToFieldNameMap(SessionCommand::class.java, "COMMAND_")
+        .mapValues { (_, value) -> value.replace("COMMAND_CODE_", "COMMAND_") }
+        .filterValues { it != "COMMAND_CUSTOM" }
 
     assertThat(MediaIntToString.sessionCommandMap).isEqualTo(expectedSessionCommandMap)
   }