Update versions in external configuration

Bump OpenAMP and libmetal. The latter is bumped a little bit
further than the latest official release, to include a bugfix
that solves some build warnings.

Signed-off-by: Jonny Svärd <jonny.svaerd@arm.com>
Change-Id: I66b735649bc6a1166b18084497628835296d77b2
diff --git a/externals.json b/externals.json
index 3cfe0dc..9be04b4 100644
--- a/externals.json
+++ b/externals.json
@@ -37,12 +37,12 @@
         {
             "path": "core_software/openamp/libmetal",
             "fetchurl": "https://github.com/OpenAMP/libmetal",
-            "revision": "v2023.04.0"
+            "revision": "8041e1c2764812a8d6feded09e68d87bc7812b3e"
         },
         {
             "path": "core_software/openamp/openamp",
             "fetchurl": "https://github.com/OpenAMP/open-amp",
-            "revision": "v2023.04.0"
+            "revision": "v2023.10.0"
         },
         {
             "path": "core_software/rtos/freertos/freertos_kernel",