[curl] Update README.fuchsia to not contain CPEPrefix

...and explicitly note that this branch is outdated and no longer
updated.

Bug: 453230021
Change-Id: If7412c142c286cf04f6b5f350aa4525bb2555570
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/curl/+/1502916
Reviewed-by: Wez <wez@google.com>

README.fuchsia

diff --git a/README.fuchsia b/README.fuchsia
index 0fbe72d..7fbe9c4 100644
--- a/README.fuchsia
+++ b/README.fuchsia
@@ -3,9 +3,14 @@
 License: MIT/X derivate
 License File: COPYING
 Upstream Git: https://github.com/curl/curl
-CPEPrefix: cpe:/a:haxx:curl:8.6.0
 Description:
 
+NOTE: This branch of the Fuchsia curl repository mirror is out of date and is no longer updated.
+Please see the README.fuchsia in the primary fuchsia.git repository found at
+`//third_party/curl/README.fuchsia`
+([link](https://cs.opensource.google/fuchsia/fuchsia/+/main:third_party/curl/README.fuchsia)) for
+the up-to-date version.
+
 Curl is a command-line tool for transferring data specified with URL
 syntax.