Add fp16_headers in allowed_deps.txt.

Fix go/apex-allowed-deps-error for aosp/1793621.

Apex-Size-Increase: 4KB for fp16_headers.a
du -h out/target/product/generic_arm64/obj/HEADER_LIBRARIES/fp16_headers_intermediates/fp16_headers.a
4.0K	out/target/product/generic_arm64/obj/HEADER_LIBRARIES/fp16_headers_intermediates/fp16_headers.a
Previous-Platform-Support: 30
Aosp-First: Yes
Test-Info: it has own unit tests

Bug: 196532440
Test: m
Change-Id: I18b9e30047f2c10fdc7c00b240be413bebfb912e
Merged-In: I18b9e30047f2c10fdc7c00b240be413bebfb912e
diff --git a/build/allowed_deps.txt b/build/allowed_deps.txt
index faeccd9..383434c 100644
--- a/build/allowed_deps.txt
+++ b/build/allowed_deps.txt
@@ -209,6 +209,7 @@
 flatbuffer_headers(minSdkVersion:(no version))
 fmtlib(minSdkVersion:29)
 fmtlib_ndk(minSdkVersion:29)
+fp16_headers(minSdkVersion:30)
 framework-mediaprovider(minSdkVersion:30)
 framework-permission(minSdkVersion:30)
 framework-permission(minSdkVersion:current)