[lex.separate] Remove last reference to instantation units

The term instantiation unit was removed by the reflection paper, P2996.

Author: AlisdairM

source/lex.tex

@@ -43,15 +43,13 @@
 
 \pnum
 \begin{note}
-Previously translated translation units and instantiation
-units can be preserved individually or in libraries. The separate
-translation units of a program communicate\iref{basic.link} by (for
-example)
+Previously translated translation units can be preserved individually or in libraries.
+The separate translation units of a program communicate\iref{basic.link} by (for example)
 calls to functions whose identifiers have external or module linkage,
-manipulation of objects whose identifiers have external or module linkage, or
-manipulation of data files. Translation units can be separately
-translated and then later linked to produce an executable
-program\iref{basic.link}.
+manipulation of objects whose identifiers have external or module linkage,
+or manipulation of data files.
+Translation units can be separately translated and then later linked
+to produce an executable program\iref{basic.link}.
 \end{note}
 \indextext{compilation!separate|)}