[dcl.fct.def.coroutine] Use 'encloses' instead of imprecise 'contains'.

The phrase 'the function-body encloses X' is also used
in [dcl.constexpr].

Author: jensmaurer

source/declarations.tex

@@ -6195,7 +6195,7 @@
 \indextext{definition!coroutine}%
 
 \pnum
-A function is a \defn{coroutine} if it contains a
+A function is a \defn{coroutine} if its \grammarterm{function-body} encloses a
 \grammarterm{coroutine-return-statement}\iref{stmt.return.coroutine},
 an \grammarterm{await-expression}\iref{expr.await},
 or a \grammarterm{yield-expression}\iref{expr.yield}.