Cleanup now that we don't need __NDK_FPABI__.

Test: tools/update_headers.sh && make checkbuild
Bug: None
Change-Id: I1b9986c4d7d5da349a8ad394e8fcf64b87c89fdf
diff --git a/libc/include/sys/cdefs.h b/libc/include/sys/cdefs.h
index 94860d9..dab252d 100644
--- a/libc/include/sys/cdefs.h
+++ b/libc/include/sys/cdefs.h
@@ -347,18 +347,6 @@
 }
 #endif
 
-/*
- * TODO(danalbert): Remove this once we've moved entirely off prebuilts/ndk.
- *
- * The NDK used to have a __NDK_FPABI__ that was defined to empty for most cases
- * but `__attribute__((pcs("aapcs")))` for the now defunct armeabi-v7a-hard ABI.
- *
- * During the transition from prebuilts/ndk to ndk_headers, we'll have some
- * headers that still use __NDK_FPABI__ while the libc headers have stopped
- * defining it. In the interim, just provide an empty definition to keep the
- * build working.
- */
-#define __NDK_FPABI__
 #if defined(__clang__)
 /*
  * Used when we need to check for overflow when multiplying x and y. This