Remove unreleased iterator library from README.md

abseil#1414

PiperOrigin-RevId: 516896705
Change-Id: Icd4ce24467ef9830ebbc68189addebb2ed1e95d4

README.md

@@ -91,9 +91,6 @@ Abseil contains the following C++ library components:
 * [`hash`](absl/hash/)
   <br /> The `hash` library contains the hashing framework and default hash
   functor implementations for hashable types in Abseil.
-* [`iterator`](absl/iterator/)
-  <br /> The `iterator` library contains utilities for augmenting ranges in
-  range-based for loops.
 * [`log`](absl/log/)
   <br /> The `log` library contains `LOG` and `CHECK` macros and facilities
   for writing logged messages out to disk, `stderr`, or user-extensible