[temp.concept] Remove redundancy: the global scope is a namespace scope.

Author: zygoloid

source/templates.tex

@@ -3886,8 +3886,7 @@
 
 \pnum
 A \grammarterm{concept-definition}
-shall appear in the global scope
-or in a namespace scope~(\ref{basic.scope.namespace}).
+shall appear at namespace scope~(\ref{basic.scope.namespace}).
 
 \pnum
 A concept shall not have associated constraints~(\ref{temp.constr.decl}).