[time.duration] Removing redundant wording, constructors and destructors can't be coroutines (since P3533R2), therefore they are always constexpr-suitable and removed wording is not needed. Also removing redundant constexpr for constructor of duration which was enforcing constexpr-ness which is now default.

Author: hanickadot

source/time.tex

@@ -1255,7 +1255,7 @@
 
   public:
     // \ref{time.duration.cons}, construct/copy/destroy
-    constexpr duration() = default;
+    duration() = default;
     template<class Rep2>
       constexpr explicit duration(const Rep2& r);
     template<class Rep2, class Period2>
@@ -1304,12 +1304,6 @@
 Members of \tcode{duration} do not throw exceptions other than
 those thrown by the indicated operations on their representations.
 
-\pnum
-The defaulted copy constructor of \tcode{duration} shall be a
-constexpr function if and only if the required initialization
-of the member \tcode{rep_} for copy and move, respectively, would
-be constexpr-suitable\iref{dcl.constexpr}.
-
 \pnum
 \begin{example}
 \begin{codeblock}