doc: clarify a case where -m/--max-count is not strictly respected

In #2843, it's requested that these trailing contextual lines should be
displayed as non-matching because they exceed the limit. While
reasonable, I think that:

1. This would be a weird complication to the implementation.
2. This would overall be less intuitive and more complex. Today, there
   is never a case where ripgrep emits a matching line in a way where
   the match isn't highlighted.

Closes #2843

crates/core/flags/defs.rs

@@ -3898,6 +3898,10 @@ When \flag{multiline} is used, a single match that spans multiple lines is only
 counted once for the purposes of this limit. Multiple matches in a single line
 are counted only once, as they would be in non-multiline mode.
 .sp
+When combined with \flag{after-context} or \flag{context}, it's possible for
+more matches than the maximum to be printed if contextual lines contain a
+match.
+.sp
 Note that \fB0\fP is a legal value but not likely to be useful. When used,
 ripgrep won't search anything.
 "