pw_span: Fix function name typo in docs

Change-Id: I204bbfe625a04e3b4e6edccb36fb220a58c66040
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/127046
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Pigweed-Auto-Submit: Alexei Frolov <frolv@google.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>
diff --git a/pw_span/docs.rst b/pw_span/docs.rst
index 8a2d1b6..d1dcd5b 100644
--- a/pw_span/docs.rst
+++ b/pw_span/docs.rst
@@ -50,7 +50,7 @@
 .. tip::
 
   Use ``pw::span<std::byte>`` or ``pw::span<const std::byte>`` to represent
-  spans of binary data. Use ``pw::as_bytes`` or ``pw::as_writeable_bytes`` to
+  spans of binary data. Use ``pw::as_bytes`` or ``pw::as_writable_bytes`` to
   convert any span to a byte span.
 
   .. code-block:: cpp