llvm-readelf only accepts `--headers`.

GNU readelf accepts both `--header` and `--headers`, but we don't ship
that in the NDK any more, so anyone on macOS or Windows will hit this
incompatibility (even though Linux users are probably still using GNU
readelf).

Test: treehugger
Change-Id: I61eb389d4d9c0bc4f5d75ceefeb5709345299585
diff --git a/android-changes-for-ndk-developers.md b/android-changes-for-ndk-developers.md
index ef5d34d..26e57b6 100644
--- a/android-changes-for-ndk-developers.md
+++ b/android-changes-for-ndk-developers.md
@@ -227,7 +227,7 @@
 information using widely-available tools.)
 
 ```
-$ readelf --header libBroken.so | grep 'section headers'
+$ readelf --headers libBroken.so | grep 'section headers'
   Start of section headers:          0 (bytes into file)
   Size of section headers:           0 (bytes)
   Number of section headers:         0