[ostream] Replace "turned on" with "set" for consistency.

Author: tkoeppe

source/iostreams.tex

@@ -6316,7 +6316,7 @@
 which can throw an exception.
 If an exception is thrown during output, then
 \tcode{ios_base::badbit}
-is turned on
+is set
 \begin{footnote}
 This is done without causing an
 \tcode{ios_base::failure}
@@ -6864,7 +6864,7 @@
 to generate the requested output.
 If an exception is thrown during output, then
 \tcode{ios_base::badbit}
-is turned on
+is set
 \begin{footnote}
 This is done without causing an
 \tcode{ios_base::failure}