Remove duplicated word 'for for' in doc

Although it is spelling mistakes, it might make an affects while reading.

Co-Authored-By: Nguyen Phuong An <AnNP@vn.fujitsu.com>
Signed-off-by: Kim Bao Long <longkb@vn.fujitsu.com>
diff --git a/doc/server_reflection_tutorial.md b/doc/server_reflection_tutorial.md
index 06a257c..acbb4a6 100644
--- a/doc/server_reflection_tutorial.md
+++ b/doc/server_reflection_tutorial.md
@@ -15,8 +15,8 @@
 
 Some platforms (e.g. Ubuntu 11.10 onwards) only link in libraries that directly
 contain symbols used by the application. On these platforms, LD flag
-`--no-as-needed` is needed for for dynamic linking and `--whole-archive` is
-needed for for static linking.
+`--no-as-needed` is needed for dynamic linking and `--whole-archive` is
+needed for static linking.
 
 This [Makefile](../examples/cpp/helloworld/Makefile#L37#L45) demonstrates
 enabling c++ server reflection on Linux and MacOS.