is_debugger_present: ptrace is not POSIX; LSB uses "tracing process"

The functionality ascribed to POSIX by the wording is not present in
POSIX. Update to reference the LSB and to use the corresponding
terminology.

Author: Hubert Tong

source/diagnostics.tex

@@ -2497,9 +2497,9 @@
 implementation returns \tcode{true} with the use of an immediate query, as
 needed, to determine if the program is being traced by a debugger. On Windows or
 equivalent systems, this can be achieved by calling the
-\tcode{::IsDebuggerPresent()} Win32 function. On POSIX, this can be achieved by
-checking for a tracer parent process, with best effort determination that such a
-tracer parent process is a debugger.
+\tcode{::IsDebuggerPresent()} Win32 function. For systems compatible with
+ISO/IEC 23360:2021, this can be achieved by checking for a tracing process, with
+best effort determination that such a tracing process is a debugger.
 \end{note}
 
 \end{itemdescr}