nodiscard-reason-only-one.C: In dg-error or dg-warning remove (?n) uses and replace .* with \[^\n\r]*.

	* g++.dg/cpp2a/nodiscard-reason-only-one.C: In dg-error or dg-warning
	remove (?n) uses and replace .* with \[^\n\r]*.
	* g++.dg/cpp2a/nodiscard-reason.C: Likewise.
	* g++.dg/cpp2a/nodiscard-once.C: Likewise.
	* g++.dg/cpp2a/nodiscard-reason-nonstring.C: Likewise.

From-SVN: r277205