Update recommended NDK to r20b in the documentation

Resolves COMPMID-5846

Signed-off-by: SiCong Li <sicong.li@arm.com>
Change-Id: I0afbcda72879ccf8e9ef486d3c4af7a3c75ba270
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/9071
Reviewed-by: Pablo Marquez Tello <pablo.tello@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/docs/user_guide/how_to_build_and_run_examples.dox b/docs/user_guide/how_to_build_and_run_examples.dox
index 81aa026..2f61f93 100644
--- a/docs/user_guide/how_to_build_and_run_examples.dox
+++ b/docs/user_guide/how_to_build_and_run_examples.dox
@@ -1,5 +1,5 @@
 ///
-/// Copyright (c) 2017-2022 Arm Limited.
+/// Copyright (c) 2017-2023 Arm Limited.
 ///
 /// SPDX-License-Identifier: MIT
 ///
@@ -184,7 +184,7 @@
  - clang++ from NDK r20b for armv8a
  - clang++ from NDK r20b for armv8.2-a with FP16 support
 
-For NDK r18 or older, here is a guide to <a href="https://developer.android.com/ndk/guides/standalone_toolchain.html">create your Android standalone toolchains from the NDK</a>:
+(From 23.02, NDK >= r20b is highly recommended) For NDK r18 or older, here is a guide to <a href="https://developer.android.com/ndk/guides/standalone_toolchain.html">create your Android standalone toolchains from the NDK</a>:
 - Download the NDK r18b from here: https://developer.android.com/ndk/downloads/index.html to directory $NDK
 - Make sure you have Python 2.7 installed on your machine.
 - Generate the 32 and/or 64 toolchains by running the following commands to your toolchain directory $MY_TOOLCHAINS: