Add libstagefright_mp3dec_headers to allowed apex deps

libstagefright_mp3dec_headers is being split out of
libstagefright_mp3dec.

Bug: 173252016
Test: m checkbuild
Change-Id: I7ab485832628203a907ebe8c3f79325d8b5788f4
diff --git a/apex/allowed_deps.txt b/apex/allowed_deps.txt
index a2f8797..a0699d8 100644
--- a/apex/allowed_deps.txt
+++ b/apex/allowed_deps.txt
@@ -383,6 +383,7 @@
 libstagefright_m4vh263enc(minSdkVersion:29)
 libstagefright_metadatautils(minSdkVersion:29)
 libstagefright_mp3dec(minSdkVersion:29)
+libstagefright_mp3dec_headers(minSdkVersion:29)
 libstagefright_mpeg2extractor(minSdkVersion:29)
 libstagefright_mpeg2support_nocrypto(minSdkVersion:29)
 libstats_jni(minSdkVersion:(no version))