Fix: add missing 'object' in [dcl.init.general]/21

In section [dcl.init.general]/21, the phrase 'Destroying a scalar type
has no effect' was missing the word 'object', making it grammatically
incomplete. The sentence should read 'Destroying a scalar type object
has no effect other than ending the lifetime of the object'.

Issue: #9346

Author: Jah-yee

source/declarations.tex

@@ -5529,7 +5529,7 @@
 or by an inherited constructor\iref{class.inhctor.init}.
 \end{note}
 Destroying an object of class type invokes the destructor of the class.
-Destroying a scalar type has no effect other than
+Destroying a scalar type object has no effect other than
 ending the lifetime of the object\iref{basic.life}.
 Destroying an array destroys each element in reverse subscript order.