Remove caveat about temporary arrays in for range loops

The optimisation to not create the array was introduced in Perl
5.005 (commit 89ea290), there's no
need to have a caveat about versions older than that any more.

Author: ilmari

pod/perlop.pod

@@ -806,15 +806,9 @@ operators depending on the context.  In list context, it returns a
 list of values counting (up by ones) from the left value to the right
 value.  If the left value is greater than the right value then it
 returns the empty list.  The range operator is useful for writing
-S<C<foreach (1..10)>> loops and for doing slice operations on arrays.  In
-the current implementation, no temporary array is created when the
-range operator is used as the expression in C<foreach> loops, but older
-versions of Perl might burn a lot of memory when you write something
-like this:
-
-    for (1 .. 1_000_000) {
-	# code
-    }
+S<C<foreach (1..10)>> loops and for doing slice operations on arrays.
+No temporary array is created when the range operator is used as the
+expression in C<foreach> loops.
 
 The range operator also works on strings, using the magical
 auto-increment, see below.