[ostream.sentry] clarify boolean expression

Eisenwave · Eisenwave · commit 2ba3cf5b9e22 · 2023-08-30T13:48:59.000+02:00
diff --git a/source/iostreams.tex b/source/iostreams.tex
@@ -6208,9 +6208,9 @@
 \tcode{os.good()}
 is
 \tcode{true},
-\tcode{ok_ == true}
+\tcode{ok_} is \keyword{true}
 otherwise,
-\tcode{ok_ == false}.
+\tcode{ok_} is \keyword{false}.
 During preparation, the constructor may call
 \tcode{setstate(failbit)}
 (which may throw
