is_debugger_present: Clarify intent to avoid false positives

The wording implies a preference to return `true` in case it is unknown
whether a debugger is present. Add a critical "only" to fix that.

Author: Hubert Tong

source/diagnostics.tex

@@ -2493,13 +2493,13 @@
 \impldef{default semantics of \tcode{is_debugger_present}}.
 
 \begin{note}
-It is intended that, when tracing the execution of a program with a debugger, an
-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
+It is intended that, using an immediate (uncached) query to determine if the
+program is being traced by a debugger, an implementation returns \tcode{true}
+only when tracing the execution of the program with a debugger. On Windows or
 equivalent systems, this can be achieved by calling the
 \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.
+a best-effort determination that such a tracing process is a debugger.
 \end{note}
 
 \end{itemdescr}