[basic.lookup.classref] Replace unnecessary use of 'indented' with 'codeblock'

Author: tkoeppe

source/basic.tex

@@ -2158,11 +2158,9 @@
 \pnum
 If the \grammarterm{id-expression} in a class member access is a
 \grammarterm{qualified-id} of the form
-
-\begin{indented}
-\tcode{class-name-or-namespace-name::...}
-\end{indented}
-
+\begin{codeblock}
+class-name-or-namespace-name::...
+\end{codeblock}
 the \grammarterm{class-name-or-namespace-name} following the \tcode{.} or
 \tcode{->} operator is
 first looked up in the class of the object expression and the name, if found,
@@ -2173,11 +2171,9 @@
 
 \pnum
 If the \grammarterm{qualified-id} has the form
-
-\begin{indented}
-\tcode{::class-name-or-namespace-name::...}
-\end{indented}
-
+\begin{codeblock}
+::class-name-or-namespace-name::...
+\end{codeblock}
 the \grammarterm{class-name-or-namespace-name} is looked up in global scope
 as a \grammarterm{class-name} or \grammarterm{namespace-name}.