Correct docs [ci skip]

We need to tighten this up depending on final approach
to these functions. At present, they certainly are not global.

l3kernel/l3box.dtx

@@ -184,23 +184,23 @@
 %     \cs{box_set_dp:Nn} \meta{box} \Arg{dimension expression}
 %   \end{syntax}
 %   Set the depth (below the baseline) of the \meta{box} to the value of
-%   the \Arg{dimension expression}. This is a global assignment.
+%   the \Arg{dimension expression}.
 % \end{function}
 %
 % \begin{function}[updated = 2011-10-22]{\box_set_ht:Nn, \box_set_ht:cn}
 %   \begin{syntax}
 %     \cs{box_set_ht:Nn} \meta{box} \Arg{dimension expression}
 %   \end{syntax}
 %   Set the height (above the baseline) of the \meta{box} to the value of
-%   the \Arg{dimension expression}. This is a global assignment.
+%   the \Arg{dimension expression}.
 % \end{function}
 %
 % \begin{function}[updated = 2011-10-22]{\box_set_wd:Nn, \box_set_wd:cn}
 %   \begin{syntax}
 %     \cs{box_set_wd:Nn} \meta{box} \Arg{dimension expression}
 %   \end{syntax}
 %   Set the width of the \meta{box} to the value of the
-%   \Arg{dimension expression}. This is a global assignment.
+%   \Arg{dimension expression}.
 % \end{function}
 %
 % \section{Box conditionals}