[diff.cpp17.class] Remove redundant cross-reference.

Author: zygoloid

source/compatibility.tex

@@ -2037,7 +2037,7 @@
 
 \diffref{class.copy.elision}
 \change
-A function returning an implicitly movable entity\iref{class.copy.elision}
+A function returning an implicitly movable entity
 may invoke a constructor taking an rvalue reference to a type
 different from that of the returned expression.
 Function and catch-clause parameters can be thrown using move constructors.