NOTES.ANDROID: fix typo in build notes

CLA: trivial
Reviewed-by: NAndy Polyakov <appro@openssl.org>
Reviewed-by: NMatthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6244)

NOTES.ANDROID

@@ -32,7 +32,7 @@
  NDK 10d:
 
     ANDROID_NDK=/some/where/android-ndk-10d
-    PATH=$ANDROID_NDK/toolchains/arm-linux-androideabi-4.8/prebuild/linux-x86_64/bin:$PATH
+    PATH=$ANDROID_NDK/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin:$PATH
     ./Configure android-arm -D__ANDROID_API__=14
 
  Caveat lector! Earlier OpenSSL versions relied on additional CROSS_SYSROOT