doc: documentation: Fix internal linking description

This commit fixes incorrect depiction of the internal link with custom
text usage.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

doc/contribute/documentation/guidelines.rst

@@ -290,11 +290,11 @@ added immediately before a heading, so the text that's displayed is the
 heading text itself. You can change the text that's displayed as the
 link writing this as::
 
-   Refer to the `show this text instead <internal-linking>`_ page
+   Refer to the `show this text instead <internal-linking_>`_ page
 
 which renders as,
 
-   Refer to the `show this text instead <internal-linking>`_ page
+   Refer to the `show this text instead <internal-linking_>`_ page
 
 
 External Cross-Reference Linking