Revert "Fixup 0cbe0d7a: avoid double redraw when completion is finished"

This is my 635th lesson that trying to be too clever is not that good.
This change interferes with the yet-to-come fix to #12674.

This reverts commit cc6dae1363.

src/mathed/InsetMathNest.cpp

@@ -2143,7 +2143,7 @@ bool InsetMathNest::insertCompletion(Cursor & cur, docstring const & s, bool fin
 		MathCompletionList::addToFavorites(inset->name());
 #endif
 		lyx::dispatch(FuncRequest(LFUN_SELF_INSERT, " "));
-	} else
+	}
 	cur.screenUpdateFlags(Update::SinglePar | Update::FitCursor);
 
 	return true;