[task.state] Fix formatting of subclause heading

Fixes NB US 248-378 (C++26 CD).

Author: jensmaurer

source/exec.tex

@@ -7306,7 +7306,7 @@
 \end{codeblock}
 \end{itemdescr}
 
-\rSec3[task.state]{\tcode{Class template \tcode{task::state}}}
+\rSec3[task.state]{Class template \tcode{task::\exposid{state}}}
 
 \begin{codeblock}
 namespace std::execution {