[temp.explicit] Remove redundant rules for contracts

given that [dcl.attr.grammar] already prohibits
attribute-specifier-seqs for an explicit instantiation.

Author: jensmaurer

source/templates.tex

@@ -6244,8 +6244,6 @@
 the \grammarterm{declaration} produced by the corresponding substitution
 into the templated function, variable, or class
 are two declarations of the same entity.
-An \grammarterm{explicit-instantiation} of a function template
-shall not specify a contract condition\iref{dcl.attr.contract}.
 \begin{note}
 These declarations are required to have matching types as specified in~\ref{basic.link}, except as specified in~\ref{except.spec}.
 \begin{example}