errwarn.cc: Clarify complex comparison warning message (bug #67257).

* errwarn.cc (warn_complex_cmp): Modify warning message to indicate that
  Matlab does not compare the co.plex part of complex numbers.
* NEWS.10.md: Note warnign message clarification.

Author: NRJank

etc/NEWS.10.md

@@ -40,6 +40,9 @@ Summary of bugs fixed for version 10.2.0 (2025-05-29):
 - Avoid parse error for empty lines in debug mode (bug #67108).
 - Check if effective SOVERSION is exported from .mex file libraries
   (bug #67163).
+- Clarify the `"Octave:language-extension" warning message for comparing
+  complex numbers that the compatibility difference is that Octave considers
+  the complex part of the number (bug #67257).
 
 ### GUI
 

libinterp/corefcn/errwarn.cc

@@ -303,7 +303,8 @@ void
 warn_complex_cmp ()
 {
   warning_with_id ("Octave:language-extension",
-                   "comparing complex numbers is not supported in Matlab");
+                   "comparing the complex part of complex numbers is not"
+                   " supported in Matlab");
 }
 
 void