[temp.param] Delete outdated wording at p15

The wording at [temp.param]/15 says:
> A template-parameter shall not be given default arguments by two
> different declarations if one is reachable from the other.

But it is conflicted with [basic.def.odr]/13:
> There can be more than one definition of a
> ...
> 	default template argument
> ...
> in a program provided that each definition appears in a different
> translation unit and the definitions satisfy the [same-meaning
> criteria of the ODR].

[temp.param] should be deleted otherwise we couldn't modularize a real
project.

Author: ChuanqiXu9

source/templates.tex

@@ -558,17 +558,6 @@
 \end{codeblock}
 \end{example}
 
-\pnum
-A \grammarterm{template-parameter}
-shall not be given default arguments by two different declarations
-if one is reachable from the other.
-\begin{example}
-\begin{codeblock}
-template<class T = int> class X;
-template<class T = int> class X { @\commentellip@ };  // error
-\end{codeblock}
-\end{example}
-
 \indextext{\idxcode{<}!template and}%
 \pnum
 When parsing a